Radiator and Cooling System
QUESTIONS
  1. A friend told me about a chemical that can be added to the radiator to make my engine run cooler.
  2. A friend told me it was improper to pour antifreeze into the radiator and then add water. Instead, he said it should be premixed before pouring it in. Why would it not just mix in the engine?
  3. A hose busted and my engine over heated. I quickly added cool water to bring the temperature down. The next day I noticed the water pump was leaking badly.
  4. A shop told me the thermostat is making the engine in my car run too cold, but my heater works fine. Is this just a ripoff?
  5. After 130,000 miles, the radiator hose on my vehicle started to leak at the clamp. I tightened the clamp, and it still leaked. I tightened it more, and the clamp broke. I replaced the clamp and now all is okay. Is this a defective or worn-out clamp?
  6. Are premixed antifreeze/coolant a better choice than concentrate and mixing my own?
  7. At what mileage should I replace my coolant?
  8. At what temperature is an engine considered to be overheating?
  9. Can a bad catalytic converter cause my radiator to overheat?
  10. Can a bad head gasket cause my radiator to break?
  11. Can a bad radiator cap cause overheating?
  12. Can a car with a blown head gasket still be driven?
  13. Can a lower temperature thermostat, for instance 180 degree in place of 195 degree, prevent overheating?
  14. Can a radiator cap cause my cooling system to over-pressurize?
  15. Can a radiator cap test good and still cause problems?
  16. Can freeze plugs be replaced without removing the engine from a vehicle?
  17. Can I prevent intake gasket problems by converting my GM vehicle to green coolant, instead of Dexcool?
  18. Can I replace the thermostat in my vehicle with one of a lower temperature?
  19. Can I used straight distilled water in my cooling system during the Summer?
  20. Can losing a freeze plug cause immediate engine damage?
  21. Can oil get into the coolant in my radiator?
  22. Coolant is leaking between the engine and transmission of my vehicle. Does this indicate a cracked engine block?
  23. Do engine thermostats go bad?
  24. Do I have to change the coolant [antifreeze] in my vehicle?
  25. Do I have to use pre-mixed coolant?
  26. Having my coolant replaced, the shop suggested I also replace the thermostat. The vehicle has 30,000 miles, does this sound right?
  27. How can a freeze plug leak?
  28. How can a radiator cap cause my car to overheat?
  29. How can I extend the life of my cooling system?
  30. How can I test an engine temperature thermostat?
  31. How does oil get into engine coolant?
  32. How much coolant should I have to add to my vehicle, before it is considered a problem?
  33. I am a chemistry student and notice all antifreeze is ethylene glycol. Why do you say it cannot be mixed or substituted?
  34. I am losing coolant and there are no external leaks. Where could the coolant be going?
  35. I failed to use antifreeze and the engine block in my car cracked. Why did the freeze plugs fail to protect the engine?
  36. I have a high mileage vehicle and my coolant is very rusty. Should I add any flush type chemicals to it?
  37. I have a leak in my radiator and have been adding water. Is it okay to keep driving as long as the radiator stays full?
  38. I have a small coolant leak, about a quart a month. Is this worth repairing?
  39. I have a very strange problem. When my radiator is full, my vehicle overheats. After the coolant gets low it quits overheating.
  40. I have an eight year old GM vehicle and have started having cooling system problems. A mechanic told me Dexcool is the cause and I should replace it with green coolant.
  41. I have an older General Motors vehicle with a 3.8L engine. I have been told the intake manifold is leaking coolant. Is it okay to continue driving as long as I continue to add coolant?
  42. I have an older GM truck with a small block V8 engine. Coolant is dripping at the rear of the engine, by the starter. Could this be a head gasket?
  43. I have had repeated cooling system problems, water pump, heater core, radiator and still the engine is over heating. Am I doing something wrong?
  44. I left the radiator cap off and my car overheated. I was told the cap got caught in the engine and caused the problem, Is this possible?
  45. I replaced a coolant hose, because my car overheated. Now the engine idles rough.
  46. I replaced my radiator and now my car idles roughly?
  47. I smell antifreeze leaking from my car, but my temperature gauge is still normal.
  48. I sometimes hear a gurgling noise coming from the dashboard area of my vehicle?
  49. I suspect a cracked head is causing the coolant loss on my Chevy Silverado. How can I detect a cracked cylinder head?
  50. I would like to replace the coolant in my vehicle, are there any special considerations?
  51. If I mix 70% coolant with 30% water will my engine run cooler than with a 50/50 mix?
  52. Is all coolant premixed?
  53. Is it possible for my car to overheat and not show it on the gauge?
  54. My car is dripping water from the bottom of the engine.
  55. My car overheats and I was told the head gasket was blown. There is no water in my oil. Can head gasket be blown and not get water in the oil?
  56. My Chevrolet 3.1L engine is losing coolant with no apparent leak. Someone suggested the intake manifold, but there is no coolant in the oil or oil in the coolant so that cannot be the problem. Where else could it be leaking?
  57. My Chevy Silverado loses coolant with no outside leak. I heard about the head cracking problem, but it does not overheat and there is no excess pressure in the radiator.
  58. My coolant reservoir indicates low about once every two months, is this normal?
  59. My Ford 4.6L engine is leaking coolant very badly at the rear of the engine.
  60. My General Motors 5.3L engine mysteriously keeps losing coolant but no one has been able to find a leak. The truck has been checked several times.
  61. My Honda Accord is overheating when sitting at an idle, but cools down when I start to drive. I was told I could remove the thermostat to solve this problem. Is this a good idea?
  62. My low coolant level light comes on when I turn my vehicle in one direction
  63. My radiator is leaking, can this be repaired?
  64. My temperature gauge goes to half-way. Does this mean my engine is over heating?
  65. My vehicle came with Dexcool antifreeze can I replace it with the regular green antifreeze?
  66. My vehicle is five years old, should I replace the cooling system hoses?
  67. My vehicle overheated due to a cracked radiator. The radiator has been replaced but it still overheats very quickly after starting and idles badly.
  68. My vehicle overheats when I am at highway speed and after driving for a long distance. I replaced the thermostat to no avail, any ideas?
  69. My vehicle temperature is normal at idle but goes down as I drive at speed, what could cause this?
  70. My vehicle's manufacturer recommends five years or 150,000 miles on the coolant change. That seems like a lot of miles, is this safe?
  71. On hard turns I hear a sloshing noise coming from the dashboard area of my vehicle. It sounds like water moving around.
  72. Recently the temperature gauge in my vehicle stays near the bottom of the scale, is this okay?
  73. Should I add water to my cooling system?
  74. Should I mix Dexcool with water before I use it?
  75. Should I use premixed coolant or regular?
  76. The belt squealed loudly on my Ford and then the engine overheated. There are no leaks but the engine gets hot when I try to drive and the heater is not working.
  77. The coolant reservoir on my vehicle kept getting low. I would fill it but it would get low again. Recently it was completely empty and I filled it. Since then it has remained full, but now I notice my temperature gauge is higher than normal.
  78. The intake gaskets on my vehicle are leaking. The shop advised this is caused by the Dexcool coolant and suggest we replace it with regular green coolant. What is your opinion?
  79. The intake gaskets on my vehicle are leaking. The shop recommends a chemical flush of the cooling system. Is this advisable?
  80. The plastic tank on my radiator is cracked. Can they be repaired?
  81. The radiator hose blew out on my car and it got really hot. I replaced the hose, but the car still gets hot every time I drive it.
  82. The radiator in my vehicle split. After being replaced one of the hoses ruptured, could there be a connection?
  83. The rear heater hose fitting pulled out of the intake manifold on my Lincoln Town Car. Can this be repaired?
  84. There is a coolant smell when I drive my vehicle, but the temperature gauge does not show hot.
  85. What is the correct temperature for my engine?
  86. What is the danger to a vehicle to continue driving when it is overheating?
  87. What is the most common cause of vehicle overheating?
  88. What is the normal operating temperature of an engine?
  89. What is the proper pH of automotive engine coolant?
  90. What is the proper ratio when mixing antifreeze with water?
  91. What is the root cause of core plug corrosion?
  92. What percentage of antifreeze to water is necessary to maintain a -34 degrees Fahrenheit freeze point?
  93. What should I do if my engine overheats?
  94. When should coolant be replaced?
  95. Which is heavier, water or antifreeze?
  96. Why does my Chevy Avalanche loose coolant when there is no apparent leak?
  97. Why does my Chevy Silverado have a gurgling noise under the dash?
  98. Why does my vehicle idle faster when it is cold?
  99. Why does the level in my vehicle coolant reservoir go up and down?
  100. Why is pre-mixed coolant less expensive than regular coolant?
  101. Why would I have to have the intake gaskets on my GM vehicle replaced twice in 80,000 miles?
  102. Why would the intake manifold on my Ford Crown Vic suddenly split open and loose all of my coolant?
  103. Why would the temperature gauge on my Chevy Silverado read very high when the engine is not overheating? Sometimes it will read all the way over when I first start the truck.
  104. Why would the water pump on my car start leaking?
  105. Will a higher pressure radiator cap help an overheating problem?
  106. Will concentrated antifreeze damage my car?
  107. Will concentrated antifreeze make an engine run cooler?
  108. Will Dexcool coolant damage my vehicle?
  109. Will pure distilled water damage my vehicle cooling system?
  110. Would removing the spring from my radiator cap help prevent overheating?
ANSWERS
  1. A friend told me about a chemical that can be added to the radiator to make my engine run cooler.

    It is not possible for a chemical to lower engine temperature on a modern vehicle. Temperature is extremely important and regulated closely by the engine computer. The thermostat and cooling fans control the temperature within a narrow range. If temperature starts to drop the thermostat closes, blocking coolant flow and the fans are switched off. If temperature is higher than normal, there is a problem. The problem should be diagnosed and corrected before driving.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


    [Back to top]
  2. A friend told me it was improper to pour antifreeze into the radiator and then add water. Instead, he said it should be premixed before pouring it in. Why would it not just mix in the engine?

    Your friend is correct. Antifreeze weighs about 9.3 pounds per gallon at room temperature. Water weights about 8.3 pounds per gallon at the same temperature. The much heavier antifreeze will settle to the lower part of the engine block. There is little circulation in that area and proper mixing is not likely.

    Without premixing, it is difficult to judge that equal portions of water and antifreeze are being added. Even if equal parts of antifreeze and water are added, they may not be distributed properly. This can result in the corrosion and freeze protection being seriously diluted, in the upper parts of the system.

    See our Detailed Topic Dexcool, coolant and proper service for even more information.


    [Back to top]
  3. A hose busted and my engine over heated. I quickly added cool water to bring the temperature down. The next day I noticed the water pump was leaking badly.

    Water pumps can easily be damaged by overheating and by thermal shock, adding a cool liquid to a hot system. Best is to let a hot engine cool naturally and only after cooling, add the proper coolant and distilled water that has been premixed.

    For more information, please see our Detailed Topic, Preventing Water Pump Problems.


    [Back to top]
  4. A shop told me the thermostat is making the engine in my car run too cold, but my heater works fine. Is this just a ripoff?

    The term cold may be a poor choice on the part of the shop. To an engine, 180 degrees Fahrenheit is considered cold. This is because most engines are designed to run at around 195 degrees and higher. If the vehicle is OBDII, 1996 or newer, it may set a check engine light for this problem. While 180 degree coolant will easily warm the passenger compartment, it can cause harm to the engine. Fuel may not be properly atomized at this temperature and the computer may request a much richer fuel-air mixture. Lower engine temperatures may cause lower fuel mileage and can contribute to wear and engine sludge buildup.

    If you are not sure about the shop, why not get a second opinion? Here’s an article on finding a great shop in your area.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


    [Back to top]
  5. After 130,000 miles, the radiator hose on my vehicle started to leak at the clamp. I tightened the clamp, and it still leaked. I tightened it more, and the clamp broke. I replaced the clamp and now all is okay. Is this a defective or worn-out clamp?
    It is not probable that a hose clamp would wear out, nor last 130,000 miles if it were defective. More likely, the rubber in the hose is starting to deteriorate, and the clamp is loose for that reason. Tightening the clamp, until it broke did not fix the problem, so more clamping force does not seem the answer. I would check the hose more closely for signs of deterioration.
    [Back to top]
  6. Are premixed antifreeze/coolant a better choice than concentrate and mixing my own?

    Often premixed coolant is better than concentrate. Premixed coolant eliminates two large problems, improper mixing and the use of water with chemical and mineral contaminates. The drawback is a much higher cost and not all types of coolant being available premixed.

    Tap water may contain many contaminates detrimental to a cooling system. Chlorine, fluoride and silica are just a few. This problem can also be prevented at a much lower cost by using distilled water. The coolant and distilled water must also be properly premixed, before putting into the system. A 50/50 mix is adequate for most applications and the coolant and water must be mixed thoroughly, before pouring into the radiator.

    Please also see our article on cooling system leaks and proper service.


    [Back to top]
  7. At what mileage should I replace my coolant?

    Deterioration of coolant is a chemical reaction and occurs over time. Mileage has much less of an affect. With most coolant, reserve alkalinity is nearly depleted in three years, with little regard to mileage. This means the pH is at or near 7.0, which is neutral. As the pH falls below 7.0 the coolant becomes acidic and starts attacking the metal components in the system. Using pH or time as a guide is much more reliable than mileage alone.

    Please see our Detailed Topic Dexcool, coolant and proper service for even more information.


    [Back to top]
  8. At what temperature is an engine considered to be overheating?

    Most modern vehicles use 195 degree Fahrenheit thermostats and operate close [10 degrees] to that temperature. Slight variances are to be expected, due to gauge differences and engine conditions. Some engines are also more tolerant than others as far as damage from overheating. As a very general guideline, temperatures over 225 degrees are normally seen as cause for concern and temperature over 245 may cause damage.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


    [Back to top]
  9. Can a bad catalytic converter cause my radiator to overheat?

    A bad catalytic converter can become plugged and severely restrict the exhaust. This can cause an engine to overheat as well as other problems.

    For more information on please see our Detailed Topic, Catalytic Converters Problems.


    [Back to top]
  10. Can a bad head gasket cause my radiator to break?

    Head gaskets fail in many different ways. If the gasket fails between a water passage and a cylinder, the coolant pressure may rise considerably and break the radiator among several other things. Radiators also just fail in time. Simple test are available to confirm the problem.

    Please also see Symptoms of a Blown Head Gasket for far more detail.


    [Back to top]
  11. Can a bad radiator cap cause overheating?

    A bad radiator cap may cause overheating and corrosion to the system as well. The boiling point of coolant is raised by adding pressure to the system. Radiator caps are designed to hold this pressure up to a pre-designed point. When they leak, pressure is lowered and the boiling point of the coolant is lowered as well.

    In addition the cap prevents evaporation, spillage and helps prevent air from entering the system. When air enters a cooling system corrosion is greatly increased. Corrosion can quickly eat through a radiator making the problem much worse. Radiator caps can be easily tested and should be replaced at any sign of a problem.
    [Back to top]
  12. Can a car with a blown head gasket still be driven?

    It is highly inadvisable to operate a vehicle with a blown head gasket. Hydrocarbons enter the cooling system and can cause extreme corrosion. Excess pressure may also occur and can over-pressure the system, causing cracked radiators and other damage. Beyond that, the engine will normally have an overheating problem, causing additional damage. Like most problems, it will be far less expensive to correct if you do not procrastinate.

    Please also see Symptoms of a Blown Head Gasket for far more detail.


    [Back to top]
  13. Can a lower temperature thermostat, for instance 180 degree in place of 195 degree, prevent overheating?

    A lower temperature thermostat will not help with overheating, assuming the original thermostat was working. A 195 degree Fahrenheit thermostat will be fully opened at normal operating temperature and have no affect on overheating. Opening at a lower temperature only causes full flow sooner. If an overheating problem exist, the vehicle will continue to overheat. To fix the symptom of overheating, the cause must be found and rectified.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


    [Back to top]
  14. Can a radiator cap cause my cooling system to over-pressurize?

    The radiator cap is simply a pressure release mechanism. It can release pressure but not create pressure by itself. Too much pressure in the cooling system is often the result of engine cylinder pressure entering the cooling system. Common causes include a cracked cylinder head or leaking head gasket.
    [Back to top]
  15. Can a radiator cap test good and still cause problems?

    The most common test of a radiator cap is the pressure test. The cap is attached to a fixture, pressure applied and the cap passes if it holds the stated amount of pressure. This is ONE test of a radiator cap but tests the lower seal and spring only. It is common for a cap to pass this test and still cause problems.

    There is also a top seal that seals the cap to the system and a vacuum valve that allows the cap to vent and still seal. These must be tested separately and many times are not tested or properly inspected. A leaking top seal will allow coolant to leak and can break the siphon effect, that allows the coolant reservoir to work.

    Radiator cap components
    [Back to top]
  16. Can freeze plugs be replaced without removing the engine from a vehicle?

    Some freeze or core plugs can be replaced with the engine still in the vehicle. There are often also freeze plugs between the engine and transmission, which would require engine or transmission removal. Others are often under brackets and accessories on the engine. Many times when replacing all freeze plugs, it is easiest to remove the engine to do a proper job.
    [Back to top]
  17. Can I prevent intake gasket problems by converting my GM vehicle to green coolant, instead of Dexcool?

    I have seen many repeat intake gasket failures on vehicles that have been converted and do not believe the coolant choice is a factor. Dexcool is a good product when properly used and replaced when depleted. Repeat intake gasket failure is more related to inferior machine work than coolant or gasket selection, in my experience.

    For much more information on leaking intake gaskets see our Detailed Topic section.
    [Back to top]
  18. Can I replace the thermostat in my vehicle with one of a lower temperature?

    There would be no point in doing this. The engine is designed to run at a specific temperature and the thermostat helps to accomplish this. If the thermostat opens at a lower temperature the vehicle computer might try to compensate by turning off the cooling fans.

    Another problem is that a colder engine burns more fuel and wears at a faster rate than an engine at normal temperature. Vehicle emissions may also be affected and the Check Engine light may come on. Stick with the vehicle manufacturer’s recommended thermostat.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


    [Back to top]
  19. Can I used straight distilled water in my cooling system during the Summer?

    Coolant/antifreeze does much more than just lower the freezing point of water. One main function of coolant is corrosion protection. Water is a corrosive and will quickly attack and destroy the various metals used in a cooling system. Aluminum turns to aluminum oxide and iron turns to ferrous oxide. These chemicals act as abrasives and further destroy the system. Only the proper coolant for the application, premixed with distilled water in a 50/50 ratio should ever be put into a cooling system.

    Please also see our article on cooling system leaks and proper service.
    [Back to top]
  20. Can losing a freeze plug cause immediate engine damage?

    For a cooling system to have enough pressure to dislodge a core plug, substantial damage likely already exist. Chances are there was a cracked cylinder head or blown head gasket. It is more likely, the core plug coming out, was a symptom and coincided with failure of an already damaged engine.
    [Back to top]
  21. Can oil get into the coolant in my radiator?

    There are a few ways oil may enter the coolant. Leaking intake gaskets are perhaps the most common cause. This is particularly common on GM vehicles. A blown head gasket or cracked cylinder head is another possible cause. This is even more likely if the engine has an over-heating problem. On many engines both coolant and oil pressure flow through the cylinder heads. Since oil pressure is normally higher than coolant pressure, oil can be forced into the coolant, when a problem exist.

    Another less common method is by radiator failure. Almost all automatic transmissions have a cooler, built into the radiator. The cooling element can rupture or crack. This may allow transmission fluid (oil) to enter the coolant. Worse, when the radiator pressure exceeds the transmission pressure, coolant enters the transmission.

    For much more information on leaking intake gaskets please see our Detailed Topic section.
    [Back to top]
  22. Coolant is leaking between the engine and transmission of my vehicle. Does this indicate a cracked engine block?

    A cracked engine block is a possibility, another may be a core plug leaking. Many engines, use metal core plugs in the rear. When the system corrodes the plug can be eaten through and leak. Normally when one plug is leaking, the others will be close to the same state. This indicates major corrosion in the system and requires immediate action to avoid further damage.
    [Back to top]
  23. Do engine thermostats go bad?

    Over time, engine thermostats may fail. This normally results in two main symptoms.

    1.) The engine will overheat, particularly when driving. This is a result of the thermostat charge-cylinder leaking or getting stuck in the closed position. The valve does not open [sufficiently] and the coolant flow is restricted.

    2.) The engine does not warm up enough or runs too cool. This normally results from a broken spring/valve or the thermostat charge-cylinder sticking open.

    These symptoms often occurs on old thermostats, after the cooling system is drained and re-filled. Many technicians advise replacing the thermostat on higher mileage vehicles, when the cooling system is serviced.

    A typical automotive engine thermostat.
    [Back to top]
  24. Do I have to change the coolant [antifreeze] in my vehicle?

    All vehicle maintenance, including coolant replacement is optional, except as required by warranty agreements. The reason to replace the engine coolant is to lessen greatly the chances of expensive cooling system problems. Performing a cooling system service will greatly reduce the risk of corrosion and damage to radiators, gaskets, heater cores, etc. The cost of a proper cooling system service is a faction of the cost of repairs it helps to prevent.

    For more information on the results of not performing maintenance, see our Detailed Topic Run Till Fail.
    [Back to top]
  25. Do I have to use pre-mixed coolant?

    You do not have to use coolant that is already premixed, but concentrated coolant must be pre-mixed with distilled water before pouring into an engine. Coolant protects from freezing and provides corrosion protection. The water in the system actually does most of the cooling. Mixing the two 50/50 provides best results in most areas and adequate corrosion protection.

    Since coolant is much heavier than water, it does not readily mix in the engine block. Premixing in the proper percentages and using distilled water prevents a great many problems.

    Please also see our article on cooling system leaks and proper service.
    [Back to top]
  26. Having my coolant replaced, the shop suggested I also replace the thermostat. The vehicle has 30,000 miles, does this sound right?

    Depending on the condition of the cooling system and the miles on the vehicle, we sometimes suggest replacing the thermostat as a preventive measure. At such low mileage, I would not recommend replacement, unless the cooling system was very corroded or there was an indication of a thermostat problem.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


    [Back to top]
  27. How can a freeze plug leak?

    Freeze plugs or more properly core plugs, normally leak because of corrosion. The metal surface on the back of the freeze plug is exposed to the coolant. Coolant or antifreeze contains corrosion protection. If the coolant is allowed to become depleted corrosion can quickly eat through the freeze plugs from the inside out. When one plug is leaking, the others are normally not far behind. Replacing all plugs can involve removing the engine and transmission in many cases.

    Leaking freeze plug or core plug caused by corrosion from weak coolant

    See our Detailed Topic Dexcool, coolant and proper service for even more information.
    [Back to top]
  28. How can a radiator cap cause my car to overheat?

    The radiator cap does more than seal the radiator. Radiator caps are also pressure control devices. The cap holds pressure on the system. As pressure increases, so does the boiling point of the coolant. For instance, pure water boils at 212 degrees Fahrenheit and at zero PSI. Adding 15 PSI raises the boil point to 249.8 degrees. Boiling water is not an efficient coolant and does not flow properly in the system. By raising the boiling point, the radiator cap helps prevent coolant from boiling and increases cooling.
    [Back to top]
  29. How can I extend the life of my cooling system?

    Three main things help to prevent cooling system problems.

    1.) Replace the coolant before the pH reaches a neutral state. Time and use reduce the pH of coolant to an acid. In time, reserve alkalinity is used up, and the coolant damages the system by corrosion. Fresh coolant has reserve alkalinity and protects against corrosion.

    2.) Monitor the coolant level and keep it full at all times. Low coolant indicates a leak and leaks cause air infiltration into the system. When air entered the cooling system, oxidation of components is greatly increased.

    3.) Replace the coolant pressure cap when it fails inspection. Most people realize a cap that leaks pressure is a problem. Caps can also fail to seal the suction side of the system. When the cap fails to seal the suction side, air may enter the system as the engine cools.

    Please also see our article on cooling system leaks and proper service.
    [Back to top]
  30. How can I test an engine temperature thermostat?

    The common method is to remove the thermostat and place it in a container, covered with water. Insert a thermometer into the water and heat. The thermostat should start to open about five degrees under the rated temperature and be fully open at the rated temperature. For instance, a typical 195 degree Fahrenheit thermostat will start to open at around 190 degrees Fahrenheit and be fully open by 195 degrees. Not opening or opening much sooner would indicate a bad thermostat.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


    [Back to top]
  31. How does oil get into engine coolant?

    One of the most common causes of oil in engine coolant is leaking intake manifold gaskets. This is particularly common of General Motors (GM) six cylinder motors such as the 3.1L, 3.4L and 3.8L. Other sources could include a bad cylinder head gasket. A radiator with an internal leak at the automatic transmission or oil cooler is another.

    For much more information on leaking intake gaskets please see our Detailed Topic section.
    [Back to top]
  32. How much coolant should I have to add to my vehicle, before it is considered a problem?

    All modern vehicles have sealed cooing systems and having to add any coolant represents a problem. The coolant level in the reservoir will rise and fall, between the normal limits, depending on temperature. Beyond normal thermal rise and fall the level should not have to be supplemented unless there is a leak.

    For information on GM 4.8L and 5.3L engines that lose coolant with no apparent leak, please see our Detailed Topic GM Coolant Loss with No Apparent Leak.
    [Back to top]
  33. I am a chemistry student and notice all antifreeze is ethylene glycol. Why do you say it cannot be mixed or substituted?

    Antifreeze (coolant) is normally ethylene glycol or propylene glycol base. This has to do with the thermal protection side of the chemical. Coolant also protects from corrosion, and this is where the differences come in. There are several means of corrosion protection employed and they are largely incompatible.

    Older coolants were generally green in color and often used silicates or phosphates to protect the metal in the cooling system. Later coolants often use organic acid or hybrid organic acid technology as well as low or no phosphates or silicates. Mixing coolants or using the improper coolant could negate corrosion protection and cause other issues such as water pump damage.
    [Back to top]
  34. I am losing coolant and there are no external leaks. Where could the coolant be going?

    The most likely scenarios are an engine leaking internally (e.g.;cracked cylinder head, leaking head gasket, leaking intake gasket, etc.) are the coolant is evaporating before you see it. Modern engine oil can hold a surprising amount of coolant without turning cloudy. Unfortunately, the oil may look normal but coolant destroys the ability to lubricate.

    Small external leaks are sometimes evaporated by the heat of the engine and do not drip. Other possible causes are a water pump that only leaks when running and the fan is dispersing the leak. Leaks at the heater core can also be difficult to find as they can drip with the evaporator water and be diluted. Adding fluorescent dye to the coolant and using a black-light might help located the source.

    For more information on GM V8 engines, please see our Detailed Topic GM Coolant Loss with No Apparent Leak.
    [Back to top]
  35. I failed to use antifreeze and the engine block in my car cracked. Why did the freeze plugs fail to protect the engine?

    The plugs used in engine blocks and cylinder heads are not actually freeze plugs at all. They are core plugs, used to remove the sand that was used in casting the engine block. They were never designed to be freeze protection. As water freezes, it expands. When a core plug pops out before the engine is damaged, it is more by luck than design.

    Typical core plug
    [Back to top]
  36. I have a high mileage vehicle and my coolant is very rusty. Should I add any flush type chemicals to it?

    I do not advocate any chemicals other than the proper coolant and distilled water, particularly in an older vehicle. The safest way to clean the system is to fully drain it, including the engine block. Fill with coolant and distilled water that has been pre-mixed. Drive the vehicle for about a week and repeat as many times as necessary.

    More frequent coolant changes can prevent a system from getting to this state. This is infinitely better, as no matter how well a system is cleaned, corrosion is difficult to stop. Worse, damage that has been done cannot readily be undone.

    See our Detailed Topic Dexcool, coolant and proper service for even more information.
    [Back to top]
  37. I have a leak in my radiator and have been adding water. Is it okay to keep driving as long as the radiator stays full?

    Continuing to add water is very unadvisable. The cooling system is susceptible to corrosion and corrosion causes tremendous damage very quickly. Water is chemically known as the universal solvent. It combines with the iron in the engine and produces ferrous oxide. Worse, it combines with the aluminum and produces aluminum oxide, an abrasive. Both of these reactions are intensified by the presence of oxygen, which enters an unsealed system.

    There is a further problem, because the system is no longer pressurized. Water boils at 212 degrees Fahrenheit at sea level. Pressure on the system raises the boiling point above the normal range of operation for the vehicle. With a crack in the radiator the system will not hold pressure. I have seen vehicles deteriorate to a point of non-economically feasible repair in a matter of months, under these conditions.

    Please see our article on cooling system leaks and proper service.
    [Back to top]
  38. I have a small coolant leak, about a quart a month. Is this worth repairing?

    I feel any coolant leak should be addressed immediately. Even small coolant leaks can have a devastating affect, over time. Each time coolant leaves the system, there is an opportunity for air to take its place. Air in the system can drastically increase corrosion. Corrosion can damage a system, beyond repair. The heater core, radiator, head surfaces, intake manifold and other components can be ruined.

    A small leak can also cause the system to lose pressure and increase the chances of overheating. By nature, leaks do not ever get better over time. Add to this the fact that you can choose the time and place of repair now. Should the vehicle breakdown on the road, you may not have that choice. Waiting will likely only increase the cost and put off the inevitable.

    Please see our Detailed Topic Symptoms and Causes of Cooling System Problems for a lot more information on coolants and corrosion.


    [Back to top]
  39. I have a very strange problem. When my radiator is full, my vehicle overheats. After the coolant gets low it quits overheating.

    To read coolant temperature, the coolant temperature sensor must touch the coolant. Some vehicles place the sensor near the top of the engine. When such a vehicle has a coolant leak, the coolant level may drop, and the sensor may lose contact with the coolant. When this occurs, the sensor may no longer show elevated temperature that exist. Continued driving is very dangerous as the vehicle can be severely damaged, even though overheating is not being indicated.
    [Back to top]
  40. I have an eight year old GM vehicle and have started having cooling system problems. A mechanic told me Dexcool is the cause and I should replace it with green coolant.

    We have serviced several-thousand GM vehicles using Dexcool and I do not find any problem with the product. There is a huge misunderstanding about Dexcool and cooling systems in general. Dexcool is an organic acid technology [OAT] coolant. This makes it different from the previous silicate type coolants. This give a slightly longer life, and I find is the source of much misunderstanding.

    GM normally states, five-years or 100,000 miles for replacing Dexcool. Like any chemical reaction, time is more important than mileage. At five years, the protection may be 100% depleted and going eight years will likely do damage, regardless of mileage. I find a more reliable indicator is pH. When the pH falls below seven, I believe damage is being done. I find this normally occurs very near five years with the original fill and around three years on subsequent fills.

    I feel two other serious causes of problems are air entering the system, due to a leak or bad radiator cap and the use of non-distilled water. What is blamed on Dexcool, almost always is a matter of one or both of the above or failure to replace the coolant in a timely manner.

    Please see our article on cooling system leaks and proper service.
    [Back to top]
  41. I have an older General Motors vehicle with a 3.8L engine. I have been told the intake manifold is leaking coolant. Is it okay to continue driving as long as I continue to add coolant?

    There is great danger in continuing to drive the vehicle. Coolant can leak into the oil or into the engine cylinders and cause tremendous damage. Many times engines are damaged beyond repair, from coolant entering the cylinders while the engine is running. I would advise immediate repair.

    It is best to replace the upper intake, which is made of plastic. The lower intake gaskets should also be PROPERLY replaced at the same time. The lower intake is made of aluminum and should be inspected and replaced if the surface area is corroded. The job should also include analysis of the oil. If any coolant contamination is found the engine crankcase should be flushed thoroughly.
    [Back to top]
  42. I have an older GM truck with a small block V8 engine. Coolant is dripping at the rear of the engine, by the starter. Could this be a head gasket?

    The GM small block engine was very robust and rarely has head gasket problems. A more likely candidate would be the intake manifold leaking and running down the rear of the engine. This was a very common issue.

    For much more information on leaking intake gaskets see our Detailed Topic section.
    [Back to top]
  43. I have had repeated cooling system problems, water pump, heater core, radiator and still the engine is over heating. Am I doing something wrong?

    You may be doing the repairs correctly, but you may not be addressing the root cause. For example, the engine you mentioned has a history of intake manifold leakage. This can be tricky to diagnose. The coolant level may drop and air may enter the system. If tap water is used to top off, rather than distilled water and if the system is not properly bled, the coolant may become corrosive. A corrosive liquid, temperature and oxygen can quickly destroy the cooling system.

    Corrosion eats away at the thin aluminum radiator and heater core. This may introduce aluminum oxide, which is a strong abrasive. This abrasive may destroy the water pump seal and hasten the demise of the radiator and core. Other aluminum components such as cylinder heads and intake base, are being attacked as well.

    Replacing the leaking water pump is simply too little, too late. The problem has not been resolved and will get worse. Continued driving can easily result in repair that exceeds the value of the vehicle.

    This scenario is almost 100% preventable. Vehicles should not need coolant added periodically. Low coolant indicates a problem and should be addressed immediately. Proper procedures of diagnosis, removal of contaminant, repair of the root cause and bleeding the system can often prevent repeated failures.

    Please also see our article on cooling system leaks and proper service.
    [Back to top]
  44. I left the radiator cap off and my car overheated. I was told the cap got caught in the engine and caused the problem, Is this possible?

    The radiator cap holds pressure on the system as well as keeping the coolant in. Leaving the cap off can cause the vehicle to overheat. It is possible a loose cap could get stuck in a radiator fan, belt drive system, damage the radiator, etc and cause further damage.
    [Back to top]
  45. I replaced a coolant hose, because my car overheated. Now the engine idles rough.

    I would be very concerned, if the rough running started after overheating the engine. Rough idle can be a sign of a blown head gasket or a cracked or warped cylinder head. The problem is often more pronounce after running the engine and then allowing the vehicle to sit for a while and then re-starting. Such damage is often caused by overheating an engine. It may be wise to have a professional test for carbon dioxide in the coolant before continuing to drive.

    Please also see Symptoms of a Blown Head Gasket for far more detail.


    [Back to top]
  46. I replaced my radiator and now my car idles roughly?

    Starting with the simplest things, it is possible something was disturbed replacing the radiator. For instance a spark plug wire or vacuum line could have been knocked loose. Another possibility is, if the battery was disconnected, the vehicle may have to re-learn idle. This may take quite a while if the throttle body is dirty.

    Coolant from when the radiator failed may have wet some ignition components such as coils, wires or spark plugs. A far more dire possibility is that the engine may have overheated, due to the radiator, and now has a blown head gasket, warped or cracked cylinder head.

    Please also see Symptoms of a Blown Head Gasket for far more detail.


    [Back to top]
  47. I smell antifreeze leaking from my car, but my temperature gauge is still normal.

    Leakage of coolant and engine temperature are related but not a direct link. Most vehicles have a coolant reservoir that accommodates the expansion of heated coolant. The reservoir can hold up to a gallon of coolant (antifreeze.) A small leak may produce the characteristic odor, but take a good while to lower the level enough to show on the gauge. This does NOT mean it is not a problem. Leaks allow air to enter the cooling system. The oxygen in the air can drastically accelerate corrosion in the system. A small leak can quickly escalate into a major repair if left unattended.

    For more information on cooling systems see our article on cooling system leaks and proper service.
    [Back to top]
  48. I sometimes hear a gurgling noise coming from the dashboard area of my vehicle?

    Gurgling noises, in that area, are often caused by air in the heater core or low refrigerant in the air conditioner evaporator. Both conditions normally indicate a leak in the system, which gets very expensive if not corrected. The vehicle should be checked and repaired immediately to avoid further problems.

    Please see our article on cooling system leaks and proper service.
    [Back to top]
  49. I suspect a cracked head is causing the coolant loss on my Chevy Silverado. How can I detect a cracked cylinder head?

    The 5.3L and 4.8L V8 engines, from 2001 through 2006 and possibly beyond, had a great many defective cylinder heads used in production. These heads tend to crack after several miles and leak coolant into the engine oil. Having the oil tested for the presence of glycol is one method. If the test is positive, the engine should be examined by an experienced technician. We have had very good results, finding this problem, by removing the valve covers and performing a pressure test. Coolant can normally be seen oozing from the crack, with close examination.

    See our Detailed Topic GM V8 Losing Coolant With No Apparent Leak for more information.
    [Back to top]
  50. I would like to replace the coolant in my vehicle, are there any special considerations?

    Newer vehicles have several concerns regarding coolant. First select the exact coolant specified by the vehicle manufacturer or equivalent. There is a multitude of different coolant formulations on the market. I recommend using the original equipment manufacturer's (OEM) brand where possible.

    Next use only clean, distilled water. Tap water may contain many contaminates, detrimental to a cooling system. Chlorine, fluoride and silica are just a few. This problem can also be minimized by using distilled water.

    I rarely recommend any type of chemical flush. Rather drain the entire system, including the engine block where possible. If the system is dirty, flush with distilled water and drain again. Systems dirtier than this would better be addressed by a professional, as other problems are likely.

    If the vehicle has high-mileage and the thermostat has never been replaced, this may also be a good time to replace it. Thermostats are inexpensive and normally easy to replace. It is also a great time to replace any hoses that need replacement.

    The coolant and distilled water must be properly premixed, before putting into the system. A 50/50 mix is adequate for most applications and they must be mixed thoroughly, before pouring into the radiator.

    It is important to check the manufacturer's procedures to see if bleeding the system is required. If so, follow the manufacturer's procedure carefully. Failure to perform this step can result in overheating and cause more corrosion than not replacing the coolant at all. Lastly, always let the vehicle come to full temperature with the cap on. Allow the vehicle to cool completely and check the level again. Many times systems will take a slight additional amount of coolant after heating and cooling.

    Please also see our article on cooling system leaks and proper service.
    [Back to top]
  51. If I mix 70% coolant with 30% water will my engine run cooler than with a 50/50 mix?

    Ironically, coolant protects the engine from freezing and corrosion. Water performs most of the heat transfer. Mixing half coolant and half distilled water (50/50) will give the best cooling and protection.

    See our Detailed Topic Dexcool, coolant and proper service for even more information.
    [Back to top]
  52. Is all coolant premixed?

    Actually only a relatively small amount of coolant comes premixed. Most coolant is concentrate and must be mixed (normally 50/50) with distilled water before use. Some people are fooled by the lower price, per gallon, of premixed coolant. While the price is less per gallon, you only get half of a gallon of coolant in a gallon. A gallon of concentrate produces two gallons of usable coolant.

    Premixed coolant is excellent to temporarily top-off a system as the mixture is always right. It is also extremely important to realize a low system means a leak. Cooling systems do not routinely need coolant added and a leak may drastically increase in cost if allowed to persist.

    Please see our article on cooling system leaks and proper service.
    [Back to top]
  53. Is it possible for my car to overheat and not show it on the gauge?

    Some engines have the temperature gauge sender unit in the intake manifold. Coolant flowing by the sender unit sends a signal that causes the gauge to respond to the temperature. If the coolant gets low, it may not reach the sender unit. The low coolant can cause the engine to overheat. Since the sender unit does not contact the coolant, the problem may not be indicated.
    [Back to top]
  54. My car is dripping water from the bottom of the engine.

    The air conditioning drips water under the vehicle as part of its normal function. This is sometimes mistaken for the engine leaking. When an engine leaks, it is often coolant or oil. Coolant could be mistaken for water, particularly if it is old and has loss the color that is added for identification.

    Coolant can leak from a number of places and will always run down and drip from a lower point. Shops normally apply pressure to the cooling system to find leaks. When the leak is very small or intermittent, dye may be added to the coolant. This will leave a trail which can be seen under black-light and with special glasses.

    The intake manifold is particularly prone to leakage on certain vehicles. This runs down the engine and can drip from the bottom. Cylinder head gaskets can also leak, as well as the water pump and hoses that are routed over the engine. Leaks coming from lower on the engine are often core (freeze) plugs. Core plugs may rust through, in a corroded system. An engine, that has water, rather than coolant in the cooling system can have all or any combination of the above. Water will quickly corrode the cooling system without the protection of coolant. Water can also freeze and crack the engine block, which will also leak.

    Please also see Symptoms of a Blown Head Gasket for far more detail.


    [Back to top]
  55. My car overheats and I was told the head gasket was blown. There is no water in my oil. Can head gasket be blown and not get water in the oil?

    Head gaskets fail in many different ways. If the gasket fails between a water passage and a cylinder or an oil passage and a coolant port, coolant and water may enter the oil. There may also be other causes for water in the oil, such as a bad intake gaskets. The head gasket might also fail and not cause such a problem, depending on the nature of the failure. Water in the oil is one possible indication of head gasket problems, but no water in the oil does NOT mean there is no failure. More testing might be in order, to confirm the problem.

    Please also see Symptoms of a Blown Head Gasket for far more detail.


    [Back to top]
  56. My Chevrolet 3.1L engine is losing coolant with no apparent leak. Someone suggested the intake manifold, but there is no coolant in the oil or oil in the coolant so that cannot be the problem. Where else could it be leaking?

    Oil in the coolant or coolant in the oil, are possible symptoms of an intake leak. Lack of these symptoms does NOT mean the intake is not leaking. Intake manifolds can also leak into the intake ports of the cylinder head. This may lose coolant but not show up as oil in the coolant or coolant in the oil.

    Other possible leaks include cylinder head gaskets or cracked cylinder heads.

    For much more information on leaking intake gaskets please see our Detailed Topic section.

    Please also see Symptoms of a Blown Head Gasket for far more detail.


    [Back to top]
  57. My Chevy Silverado loses coolant with no outside leak. I heard about the head cracking problem, but it does not overheat and there is no excess pressure in the radiator.

    The cylinder-head cracking problem, on the 4.8L and 5.3L engines, is not in the combustion chamber. The area that tends to crack is in the rocker arm area. Since this area of the cylinder head is not pressurized by the combustion chamber, coolant leaks into the oil. There is usually no external symptoms other than coolant loss and the inevitable failure of the engine, if not repaired.

    See our Detailed Topic GM V8 Losing Coolant With No Apparent Leak for more information.
    [Back to top]
  58. My coolant reservoir indicates low about once every two months, is this normal?

    It is not normal for a late model vehicle to need any coolant added to the system. This indicates a leak, and can be an extremely hazardous condition. Losing coolant can cause air to enter the system and result in extreme corrosion. Worse, coolant can leak into the engine oil. Even small amounts of coolant in the oil, difficult for a laboratory to trace, can severely damage an engine.

    The system should be checked and repaired before driving further. The normal procedure involves pressurizing the system and inspecting for leaks. Smaller leaks sometimes require that a fluorescent dye be added and the system inspected with a special light.
    [Back to top]
  59. My Ford 4.6L engine is leaking coolant very badly at the rear of the engine.

    A common failure on these engines, is the plastic intake manifold. They tend to crack in the front, behind the alternator and at the rear heater hose nipple. There was a class action suite against Ford and they had to reimburse a lot of folks for these problems. Unfortunately, the time has expired to receive reimbursement.

    Pressure testing the system should reveal the exact source of the leak. Follow the heater hose to the point where it attaches to the intake. Slightly moving the hose will often show the source of the leak.

    For more information, please see our Detailed Topic, Ford 4.6L Plastic Intake Manifold Problems.


    [Back to top]
  60. My General Motors 5.3L engine mysteriously keeps losing coolant but no one has been able to find a leak. The truck has been checked several times.

    This cooling system is sealed, if there is coolant loss there will be a leak. Cracked cylinder heads are often overlooked and can be hard to diagnose. From 2001 till 2006 and possibly beyond, the 4.8L and 5.3L GM engines had a problem with cylinder head cracking. Defective castings were used and can crack after several miles of use. Having the oil tested for the presence of glycol will normally indicate the problem. An experience technician can also normally spot the problem by removing the valve covers.

    Please see our Detailed Topic GM V8 Losing Coolant With No Apparent Leak for more information.
    [Back to top]
  61. My Honda Accord is overheating when sitting at an idle, but cools down when I start to drive. I was told I could remove the thermostat to solve this problem. Is this a good idea?

    ABSOLUTELY NOT! The engine thermostat is crucial to engine operation and life. It should never be removed or replaced with one of a different temperature. If the thermostat were bad, it should be replaced with a new one of the exact type. The vehicle should not continue to be driven as tremendous damage can be done by overheating.

    Overheating problems at idle that go away when driving are not likely a thermostat issue. A more likely cause would be fan operation. Check to see if the cooling fan(s) are coming on. If the fans are not running, when the engine is hot, repair them before going on.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


    [Back to top]
  62. My low coolant level light comes on when I turn my vehicle in one direction

    A low coolant light on turns, is often caused by low coolant, sloshing on turns, moving away from the sensor. A full reservoir does not always indicate a full radiator. Once the system gets low, the siphon can be loss and the reservoir may no longer indicate radiator level. Check the coolant, in the radiator, after allowing the vehicle to cool for several hours. Remove the radiator cap and make sure the coolant is full to the top of the neck. Also be aware that a low radiator indicates a leak. Continuing to add coolant may allow air to enter the system and cause tremendous corrosion problems.
    [Back to top]
  63. My radiator is leaking, can this be repaired?

    Virtually all radiators today are made of aluminum and plastic. They normally leak for two reasons. Over time, the plastic tanks crack. This occurs because the plastic becomes brittle. A second reason is the aluminum core has corroded and a hole has developed. In neither case is repair a very good option. Most repair will be very short lived and replacement is normally an overall lower cost option.
    [Back to top]
  64. My temperature gauge goes to half-way. Does this mean my engine is over heating?

    A reading of half way does not necessarily indicate a problem. More important is the actual temperature of the engine. Each gauge is calibrated differently and half way is normal on many vehicles. Normal operating temperature is around 200 degrees Fahrenheit on most modern vehicles. A problem is normally indicated when the temperature exceeds 225 degrees Fahrenheit. With no numbers, if the gauge moves higher than the position where it has typically run, a problem is likely.
    [Back to top]
  65. My vehicle came with Dexcool antifreeze can I replace it with the regular green antifreeze?

    Dexcool and many other specialty coolants [antifreeze] are not the same as the standard green coolant. Modern vehicles have a variety of metals in the cooling system and are designed to work best with the coolant supplied by the manufacturer. I always recommended replacing coolant with the same coolant, originally supplied by the manufacturer.

    AGCO uses pure distilled water, premixed with the proper coolant in out client's cooling systems. Tap water can contain several chemicals and minerals that may damage a cooling system.

    Many vehicles also have a specific bleeding procedure, to remove air from the system, when serviced. Failure to properly bleed the system can result in overheating, and severe corrosion problems. Always consult a service manual and follow the procedure carefully if you decide to replace your own coolant [antifreeze].

    Please see our Detailed Topic Dexcool, coolant and proper service for even more information.
    [Back to top]
  66. My vehicle is five years old, should I replace the cooling system hoses?

    Coolant hoses, on newer vehicles, last much longer than they used to. Some hoses are still like new even after five years of service. Complicating the matter further, some aftermarket hoses are of much lower quality than the originals. Replacing good original hoses with lower grade aftermarket hoses may be worse than not replacing them. Having the hoses inspected annually, after the first four years, is safe. Any hose that has hardened, softened, cracked, bulged or is otherwise showing wear should then be replaced.
    [Back to top]
  67. My vehicle overheated due to a cracked radiator. The radiator has been replaced but it still overheats very quickly after starting and idles badly.

    The engine should be tested for carbon dioxide, present in the coolant. This simple test will often reveal a blown head gasket or cracked cylinder head. This type damage is often the result of overheating, as little as one time. Once hydrocarbons begin entering the coolant the engine will normally continue to overheat. Coolant can also leak into the cylinders, causing a rough idle or misfire.

    The longer this is allowed to occur the greater the chance of damage to the engine and other components. Coolant entering the exhaust can also result in damage to catalytic converters and oxygen sensors

    Please also see Symptoms of a Blown Head Gasket for far more detail.


    [Back to top]
  68. My vehicle overheats when I am at highway speed and after driving for a long distance. I replaced the thermostat to no avail, any ideas?

    One possible cause is a partially plugged radiator that flows adequately for low load use but cannot tolerate higher heat loads. You may have to have the radiator flow tested to determine if this is the cause.

    Another possibility could be combustion gasses leaking into the coolant. There are tests that can be run to try to determine this.

    Please also see Symptoms of a Blown Head Gasket for far more detail.


    [Back to top]
  69. My vehicle temperature is normal at idle but goes down as I drive at speed, what could cause this?

    Lack of engine temperature will almost always be related to the engine thermostat. When an engine is below temperature the thermostat closes and blocks the coolant flow. If the thermostat is stuck open or opens at too low a temperature, the engine will not warm up. At idle, the water pump turns slowly and the cooling fans will not come on at low temperature. This may allow the engine to warm up, even without the thermostat being closed. At speed, the water pump turns faster and air is flowing through the radiator. Under these conditions, the thermostat would need to operate to maintain temperature.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


    [Back to top]
  70. My vehicle's manufacturer recommends five years or 150,000 miles on the coolant change. That seems like a lot of miles, is this safe?

    Antifreeze or coolant breakdown is a chemical process and occurs 24 hours a day and whether the vehicle is driven or sitting idle. Here the years are more critical than the miles. At five years the coolant is very near total depletion and corrosion may be occurring. Going beyond five years, even with much lower mileage may cause considerable damage.

    Checking the specific gravity, measured by a refractometer and the pH level is a far better guide. We have found this to be far more helpful in preventing damage to cooling systems than the mileage/years method.

    It is also important to remember that the manufacturer's recommendation only applies to the initial fill, in a new vehicle and not subsequent change intervals. In our experience replacement at three years or when pH reaches 7.0 gives far better economy, when repair cost is considered.

    Please see our Detailed Topic Dexcool, coolant and proper service for even more information.
    [Back to top]
  71. On hard turns I hear a sloshing noise coming from the dashboard area of my vehicle. It sounds like water moving around.

    Often, such noise is caused by water trapped in the evaporator drain pan. The pan catches the water that naturally condenses on the evaporator and drains it outside the vehicle. If the drain becomes plugged, the water can be trapped. If the pan overflows water may enter the passenger compartment and damage the vehicle interior.

    A leaking heater core may also cause the drain to plug and the sloshing noise. In either case, having the vehicle checked and repaired can prevent further problems. Please see our article on cooling system leaks and proper service.
    [Back to top]
  72. Recently the temperature gauge in my vehicle stays near the bottom of the scale, is this okay?

    An engine running too cool is almost as bad as running too hot. Low temperature will increase fuel consumption, wear, emissions and sludge build up in the engine. In almost every case the problem of running too cool is related to the engine thermostat. The problem should be diagnosed and corrected immediately to prevent problems.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


    [Back to top]
  73. Should I add water to my cooling system?

    Water and coolant should be mixed in a ratio, normally 50/50, to protect the engine properly. Adding water to the system dilutes the corrosion protection and may cause severe problems. Testing the specific gravity of the mixture determines the actual ratio if needed. Best is to only add coolant and distilled water that has been premixed.

    Please see our Detailed Topic Symptoms and Causes of Cooling System Problems for a lot more information on coolants and corrosion.


    [Back to top]
  74. Should I mix Dexcool with water before I use it?

    Dexcool is normally sold as a concentrate and should be mixed with distilled water, before adding to the cooling system. There are also coolants on the market, listed as Dexcool compatible, that might be pre-mixed, that is already contain water. Always read the label to be sure.
    [Back to top]
  75. Should I use premixed coolant or regular?

    Most important is to get the proper coolant that is specified for the vehicle. There are many universal coolants on the market which are of questionable worth, in my opinion. As long as you have a means to properly mix coolant and distilled water, 50/50 before adding to the system, concentrate is far less expensive. If not, premix will at least insure that you have the proper mixture in the system. It is also quite a bit easier to use. Premix is also great for adding coolant to a system that might be leaking, until it can be repaired.

    Please see our article on cooling system leaks and proper service.
    [Back to top]
  76. The belt squealed loudly on my Ford and then the engine overheated. There are no leaks but the engine gets hot when I try to drive and the heater is not working.

    Some Ford engines use water pumps with plastic impellers. It is not uncommon for the impeller to break. When this happens it can jamb the pump and cause the belt to squeal. A broken impeller will also not push coolant through the system resulting in overheating and no heat from the heater. Broken impeller pieces may also cause problems with the thermostat and heater core. During repair, be sure the check for debris left in the cooling system, as it may cause a recurrence of the problem.
    [Back to top]
  77. The coolant reservoir on my vehicle kept getting low. I would fill it but it would get low again. Recently it was completely empty and I filled it. Since then it has remained full, but now I notice my temperature gauge is higher than normal.

    You should stop driving the vehicle immediately and have the cooling system checked. Driving with a coolant leak may do extreme damage should the coolant leak into the oil or run low. Likely there is air in the radiator from when the reservoir lost all its contents. This breaks up the syphon that makes the reservoir work. It may now stay full even though the radiator is dangerously low.

    Please see our article on cooling system leaks and proper service.
    [Back to top]
  78. The intake gaskets on my vehicle are leaking. The shop advised this is caused by the Dexcool coolant and suggest we replace it with regular green coolant. What is your opinion?

    I disagree and have seen no evidence that Dexcool is involved in intake gasket failure. We have repaired a great many of these vehicles. Many were previously repaired at other shops and converted to standard coolant. I feel the problem is an excessively rough surface finish on the cylinder heads and intake surface. The vehicles we treat by addressing the surface finish, have shown no repeat incidence of failure and all use the Dexcool coolant.

    For much more information on leaking intake gaskets see our Detailed Topic section.
    [Back to top]
  79. The intake gaskets on my vehicle are leaking. The shop recommends a chemical flush of the cooling system. Is this advisable?

    Most cooling system leaks are the result of corrosion. Most corrosion comes from improper cooling system maintenance and service. I very rarely advise adding chemicals to a cooling system. At best, they will not solve the original problem. At worst they will further damage the system. I feel the best way to clean contaminants from the cooling system is with complete draining, refilling and bleeding, several times. To stop corrosion the root cause must be found and corrected.

    For much more information on leaking intake gaskets see our Detailed Topic section.
    [Back to top]
  80. The plastic tank on my radiator is cracked. Can they be repaired?

    Repair of plastic radiators are not practical. After an average of eight to 12 years, the heat/cool cycles take a toll. The plastic loses its flexible nature and cracks. Replacing the tanks cost almost as much as a replacement radiator and the core is still old and worn. Adhesive patches are also ineffective as they will not adhere to the hot, brittle plastic. A new replacement is always the least expensive option.
    [Back to top]
  81. The radiator hose blew out on my car and it got really hot. I replaced the hose, but the car still gets hot every time I drive it.

    Over heating an engine, even one time, can cause a great deal of additional damage. Head gaskets fail and cylinder heads may warp and even crack. Once these problems begin, combustion hydrocarbons enter the cooling system and the vehicle quickly overheats. Each time the vehicle is over heated the situation gets worse. A carbon dioxide test can help diagnose this situation.

    It is also possible you had more than one problem initially. For instance, cooling fans not working can cause an overheat and cause a weak hose to blow. Repairing the hose could have been treating a symptom of the original problem. Only a proper system test will say for certain, but continuing to drive the vehicle will greatly increase the odds of serious problems

    Please also see Symptoms of a Blown Head Gasket for far more detail.


    [Back to top]
  82. The radiator in my vehicle split. After being replaced one of the hoses ruptured, could there be a connection?

    Both are symptoms of over-pressurization of the system. This is often caused by a blown head gasket or a cracked cylinder head. Two simple test are available that may be able to diagnose these problems. The first is a carbon dioxide test, where the cooling system is checked for the presence of carbon dioxide. Note that a positive result indicates a definite problem. A negative result does NOT mean that a problem does not exist, only that it is not being revealed. The second test is a pressure-rise test, where pressure in the system is measured, over time and at different engine RPM.
    [Back to top]
  83. The rear heater hose fitting pulled out of the intake manifold on my Lincoln Town Car. Can this be repaired?

    Unfortunately the only repair that will last, is manifold replacement. The problem is with the material used in construction of the intake. From 1996 through 2001 Ford had a problem with their plastic intakes. After losing a class action suite they reimbursed customers for a short while and offered a slightly extended warranty on the intake. Both have ended but the 2002 intake was updated and can be retrofitted to prevent recurrence of the problem.

    For more information, please see our Detailed Topic, Ford 4.6L Plastic Intake Manifold Problems.


    [Back to top]
  84. There is a coolant smell when I drive my vehicle, but the temperature gauge does not show hot.

    Cooling systems normally have a reservoir which may hold up to an extra gallon of coolant. This is designed to accommodate the expansion and contraction of coolant as it heats and cools. With a small leak, it also tends to replenish the system temporarily. A coolant smell indicates a leak. Chances are, the level has not gotten low enough to cause overheating, which is good. The system should be checked and repaired immediately to avoid major problems.

    Please see our article on cooling system leaks and proper service.
    [Back to top]
  85. What is the correct temperature for my engine?

    Almost all modern vehicles use a 195 degree Fahrenheit thermostat. This will place normal operating temperature around 200 to 205 degrees. Consistent temperature over 225 or under 195 degrees Fahrenheit is usually cause for concern.

    For more information, please see our Detailed Topic, Engine Thermostats, Fuel Mileage and Over Heating.


    [Back to top]
  86. What is the danger to a vehicle to continue driving when it is overheating?

    Continuing to Drive an overheating vehicle will always result in engine and possibly automatic transmission damage. When metal overheats it expands. The tight tolerances within the engine, close up and lubricant can no longer work. Head gaskets are crushed and often start to leak, making the overheating much worse. Continued overheating will also crack cylinder heads and can gall cylinder walls. Since the automatic transmission fluid is cooled by the same radiator transmission damage can also occur.

    Please also see Symptoms of a Blown Head Gasket for far more detail.


    [Back to top]
  87. What is the most common cause of vehicle overheating?

    The most common cause of overheating, is leaks in the system, that cause a loss of coolant. The most common cause of leaks is corrosion, caused by weak or inadequate coolant and air entering the cooling system through leaks.
    [Back to top]
  88. What is the normal operating temperature of an engine?

    The normal operating temperature of a modern automobile engine is around 200 degrees Fahrenheit. This is the average temperature of the coolant. Actual temperature depends on where it is measured. Cylinder head temperature is normally greater and lower engine temperature may be cooler.
    [Back to top]
  89. What is the proper pH of automotive engine coolant?

    New coolant normally runs around 8.0 to 8.5. This alkaline state is called reserve alkalinity. As coolant ages, the pH will drop or become more acidic. The neutral state regarding pH is 7.0 which is neither acidic nor alkaline. When this state is reached, the coolant should be replaced. Coolant that reaches an acidic state will greatly increase the chances of corrosion in the cooling system.
    [Back to top]
  90. What is the proper ratio when mixing antifreeze with water?

    For almost any situation half antifreeze [coolant] and half distilled water is optimum. This 50/50 mix provides good freeze protection, cooling and corrosion protection.

    Please see our Detailed Topic Dexcool, coolant and proper service for even more information.
    [Back to top]
  91. What is the root cause of core plug corrosion?

    Core plugs, also called freeze plugs are exposed to the engine coolant. They corrode for the same reasons anything else in the system corrodes. Most common is depleted or improperly mixed coolant. Coolant provides corrosion protection for the system, but must be properly mixed and replaced when depleted.

    Please see our Detailed Topic Dexcool, coolant and proper service for a lot more information on coolants and corrosion.
    [Back to top]
  92. What percentage of antifreeze to water is necessary to maintain a -34 degrees Fahrenheit freeze point?

    Most experts agree, a concentration of 50 percent distilled water and 50 percent antifreeze will offer freeze protection to -34 degrees Fahrenheit. A 50/50 concentration also offers good corrosion protection and adequate cooling.

    % Antifreeze Freeze Point Fahrenheit

    10%

    25 degrees F

    20%

    16 degrees F

    25%

    10degrees F

    30%

    4 degrees F

    35%

    -3 degrees F

    40%

    -12 degrees F

    45%

    -22 degrees F

    50%

    -34 degrees F

    60%

    -48 degrees F

    65%

    -62 degrees F


    [Back to top]
  93. What should I do if my engine overheats?

    From a mechanical standpoint, the best thing is to shut it off and allow it to cool. Never try to remove the radiator cap or add water to a hot system. Removing the cap can result in severe burns and losing coolant pressure can cause the coolant to boil. After the engine is completely cool, check the coolant by removing the cap. Add only the proper coolant, premixed with distilled water to the system. Adding water alone, will dilute the corrosion protection and can cause severe damage.
    [Back to top]
  94. When should coolant be replaced?

    The exact interval varies depending on many factors. Of primary consideration is the freeze point, which can be measured with a refractometer or specific gravity tester. Equally important is the pH which should remain alkaline (above 7) at all times. When the reserve alkalinity is depleted the coolant can become acidic very quickly and inflict severe damage on the cooling system.

    Cleanliness of the coolant and rust or also important factors. My experience has shown that mileage does not affect these things as much as time. I recommend not exceeding three years for best overall economy.

    See our Detailed Topic Dexcool, coolant and proper service for even more information.
    [Back to top]
  95. Which is heavier, water or antifreeze?

    Antifreeze is considerably heavier than water and should always be premixed with water before pouring into an engine.
    [Back to top]
  96. Why does my Chevy Avalanche loose coolant when there is no apparent leak?

    A common cause of leakage on the 4.8L and 5.3 liter engines, used in the Avalanche, is cracked cylinder heads. GM used an inferior casting on many of these heads and they tend to develop cracks. The leak often starts around 100,000 to 130,000 miles and shows no external signs. We use a fluorescent dye in the coolant to identify the source. Replacement of the cylinder head(s) is the remedy and left without repair engine damage will quickly follow. The Silverado, Sierra, Tahoe and other vehicles using this engine also frequently see the same issue.

    Please see our Detailed Topic GM V8 Losing Coolant With No Apparent Leak for more information.
    [Back to top]
  97. Why does my Chevy Silverado have a gurgling noise under the dash?

    Most gurgling noise is the result of air in the heater core. Air enters the heater core when the system is low on coolant or improperly serviced. The Silverado is a self bleeding system and should purge the air, if the coolant leak is corrected and the system is properly filled.

    Sometimes noise persist after repairing and filling the system. Corrosion [from the air] can plug the purge line. Check the hose that runs from the top of the radiator to the purge reservoir. With the engine running, coolant should be flowing back to the purge reservoir. If not check for a restriction in the line or nipple.
    [Back to top]
  98. Why does my vehicle idle faster when it is cold?

    Engines are optimized to run above a certain (normally about 195 degrees Fahrenheit) temperature. Below that temperature engines do not run as efficiently. By raising idle speed this is overcome, saving fuel, improving drive-ability and reducing emissions. The higher idle speed, when the engine is cool, also boost oil pressure slightly and better lubricates the engine.
    [Back to top]
  99. Why does the level in my vehicle coolant reservoir go up and down?

    Coolant expands when it removes heat from the engine. The expansion is handled by the coolant reservoir, which rises to the maximum (MAX) mark. When the coolant gives off the heat and cools, the level drops to the minimum or (MIN) mark. If the coolant remains between the two marks everything is normal. Dropping below the minimum mark is not normal and indicates a leak in the system.

    proper coolant level when engine is fully warmed
    [Back to top]
  100. Why is pre-mixed coolant less expensive than regular coolant?

    Actually premixed coolant is quite a bit more expensive. The price of a gallon may be less, but remember a gallon of concentrated antifreeze produces two-gallons of water/coolant mix at 50/50. Premix offers some advantages, despite the higher price. One is convenience. It is already mixed perfectly with distilled water. This is perfect for adding coolant to a system. It is also infinitely better than the common practice of merely adding water. Premixed coolant keeps the mixture at 50/50, where it needs to be for corrosion protection. It also helps to prevent contaminants, from tap water from entering the system.

    Please see our article on cooling system leaks and proper service.
    [Back to top]
  101. Why would I have to have the intake gaskets on my GM vehicle replaced twice in 80,000 miles?

    Leaking intake gaskets on GM vehicles are a symptom and not THE problem. A great many shops simply treat the symptom, that is replace the gaskets. Doing so will all but guarantee an encore performance of the issue.

    We have done quite a bit of research into the problem. In every case of repeat failure I have found excessively rough or uneven mounting surfaces. This is the machined surface of the cylinder heads and lower intake manifold. Sometimes coolant was not replaced [properly] and corrosion damaged the surface. In other cases the shop damages the surfaces by improper methods. Many times the original machine work is too rough to allow a proper seal.

    Without smooth [60 micro inch or better] surfaces that are flat, lacking pits, clean and properly assembled, the job will not last.

    For much more information on leaking intake gaskets see our Detailed Topic section.
    [Back to top]
  102. Why would the intake manifold on my Ford Crown Vic suddenly split open and loose all of my coolant?

    From 1996 through 2001 Ford had a problem with their plastic intakes. After losing a class action suite they reimbursed customers for a short while and offered a slightly extended warranty on the intake. Both have ended but the 2002 intake was updated and can be retrofitted to prevent recurrence of the problem.

    For more information, please see our Detailed Topic, Ford 4.6L Plastic Intake Manifold Problems.


    [Back to top]
  103. Why would the temperature gauge on my Chevy Silverado read very high when the engine is not overheating? Sometimes it will read all the way over when I first start the truck.

    The 2003 through 2006 GM truck instrument panel cluster (IPC) was under recall up to 70,000 miles for this and other gauge failures. This includes the Silverado and the GMC Sierra. Though not recalled several other GM vehicles use the same parts and have the same problem. The cause is inferior stepper motors used in building the instrument panels. To have the vehicle repaired under the recall, you would have to return to a GM dealership. If you are out of the recall mileage, AGCO can replace the defective stepper motors with updated motors at a much lower cost.

    See our Detailed Topic article GM Dash Gauge Failure for far more details.
    [Back to top]
  104. Why would the water pump on my car start leaking?

    Water pumps are mechanical devices and are subject to wearing out. The water pump is turning whenever the engine is running, but unlike the engine does not have a pressurized lubrication system. Instead the water pump depends on the engine coolant for lubrication.

    Premature (before 100,000 mile) failure is often caused by allowing the coolant to deteriorate. Dirty, weak or acidic engine coolant can attack the water pump. The wrong type of coolant can also damage a water pump. Most engines today use specific coolant types and using the wrong type can cause damage.

    For more information, please see our Detailed Topic, Preventing Water Pump Problems.


    [Back to top]
  105. Will a higher pressure radiator cap help an overheating problem?

    Radiator caps are designed for a pressure, compatible with the entire system. Raising the pressure can damage other components and does not address the cause of the overheating. It can also be dangerous and create other problems. Best is to have the overheating problem diagnosed, corrected and only use the proper pressure radiator cap on the system.
    [Back to top]
  106. Will concentrated antifreeze damage my car?

    Antifreeze or coolant is designed to prevent corrosion, lower the freeze point and raise the boil point of water. Water is the actual cooling agent and must be used, normally in a 50/50 mix with coolant. Concentrated antifreeze will not properly cool the engine and can cause damage.

    Please see our Detailed Topic Symptoms and Causes of Cooling System Problems for a lot more information on coolants and corrosion.


    [Back to top]
  107. Will concentrated antifreeze make an engine run cooler?

    To the contrary, antifreeze [coolant] protects from freezing, corrosion and helps prevent boiling of water. Water is the actual cooling agent. Without water the engine may overheat and without antifreeze/coolant, corrosion will quickly destroy the cooling system. A blend of fifty-percent distilled water and fifty-percent antifreeze will provide the best results in most environments. In extreme cold slightly more antifreeze will reduce the freeze point.
    [Back to top]
  108. Will Dexcool coolant damage my vehicle?

    GM has used Dexcool in millions of vehicles since 1996 and I have never seen a problem when used as instructed. The claims against the coolant, that I have seen, seem misdirected by misunderstanding the causes of the problems. The cooling system problems associated with GM vehicles are more a problem of poor workmanship and poor service practices, in my experience.

    See our Detailed Topic Dexcool, coolant and proper service for even more information.
    [Back to top]
  109. Will pure distilled water damage my vehicle cooling system?

    Water, whether distilled are otherwise, will severely corrode a cooling system. Coolant (antifreeze) provides corrosion protection, raises the boil point and lowers the freeze point when properly mixed with distilled water. Straight water or straight coolant should NEVER be added to an automotive cooling system.

    Please see our Detailed Topic Symptoms and Causes of Cooling System Problems for a lot more information on coolants and corrosion.


    [Back to top]
  110. Would removing the spring from my radiator cap help prevent overheating?

    An engine over heating is a symptom and always has a cause. Only by diagnosing and correcting the cause will the symptom of overheating be alleviated. The spring loaded cap raises pressure in the cooling system which raises the boiling point of the coolant. Reducing system pressure will only result in coolant that boils at a lower temperature.
    [Back to top]
Jump to:
View all categories
Printable view