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Cooling System

Thermostat Temperature

Q: The thermostat that's in my car right now is 160 degrees. My friend told me to put in a 195 degree thermostat. Isn't it better to have the engine running cooler?

A: The powertrain control module (computer) and other engine sensors are designed to maintain the best combustion efficiency when the engine is at the optimal operating temperature. The purpose of the thermostat is to get the engine up to and maintain the optimal temperature. You should find out the temperature of thermostat that was originally installed in the vehicle and stick with that. Go to your local auto parts store and they can tell you. Most automobiles have a 195 degree Fahrenheit thermostat installed from the factory. Installing the incorrect thermostat can decrease fuel economy.

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A/C Compressor

Q: What are the steps for installing an A/C Compressor?

A: You should not perform this type of repair unless you have a special machine that can recover and recycle the refrigerant and you have been trained and certified to perform this type of procedure. Depending on the type of refrigerant, releasing it into the atmosphere could contribute to ozone depletion and/or enhance global warming. The most common automotive refrigerants are R-12 and R-134a. R-12 refrigerant was used extensively in automobiles until the early 1990's. R-134a, a more environmentally friendly refrigerant, was phased in to replace R-12, however its release still impacts global warming. It is against the law for technicians to intentionally release refrigerants into the air. Service technicians are required by law to recover and recycle refrigerants.

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Antifreeze as a Coolant

Q: I recently had a radiator hose burst and lost all my antifreeze. Since warm weather is here I thought I would just run pure water in the engine for the summer. Will this hurt the engine?

A: Antifreeze is also a coolant and is important in warm as well as cold seasons. Pure water will boil at 212 degrees Fahrenheit and can be corrosive within the engine. Most automotive manufacturers require a 50% water to 50% antifreeze solution all year. The boiling temperature will increase to 226 degrees Fahrenheit with the 50/50 concentration and reduce the likelihood of overheating your engine. Antifreeze also reduces corrosion. Different types of antifreeze exist, so be sure you use the type your vehicle manufacturer recommends and flush as required. Since antifreeze is a hazardous waste, recycle it according to local laws.

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Antifreeze Loss

Q: We were driving yesterday on the highway and the check engine light went on. When we pulled off the road we found antifreeze all over top of engine like something exploded. What could this be?

A: It could be something as simple as a radiator or heater hose that has burst. Another possibility is a frost plug or engine block heater popping out. Or, it could be as complex as a cracked cylinder head, faulty head gasket, or damaged engine block causing the problem. Do not drive the car. The vehicle should be towed to your service center. Driving the car without antifreeze will damage the engine further.

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Antifreeze vs. Water

Q: What will happen if my car only has water in the radiator and gets cold enough to freeze?

A: If it gets cold enough, the frozen water (since it expands) could crack the block, radiator, or water pump. You need to have the water drained and replaced with a 50% water to 50% antifreeze mixture. This will protect your engine down to -34 degrees Fahrenheit.

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Blown Head Gasket

Q: I recently had the oil changed in my car and they tell me they think that antifreeze is leaking into the oil. Could you tell me how this would happen?

A: A worn head gasket, cracked engine block, or cracked head could cause antifreeze/coolant to enter the oil system. Check to see if you are losing antifreeze over time or if the antifreeze is also contaminated with oil. You can have your car's fluids tested at a lab to confirm the diagnosis. Another sign is excessive white smoke coming from the tailpipe. Overheating the engine is the most common cause for failure of the head, engine block, or head gasket.

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Coolant Smells Like Oil

Q: There is a smell of oil in radiator. The coolant looks dark and muddy. I have 86,000 miles on the vehicle and it has never been flushed.

A: I would recommend having the radiator flushed and refilled with the proper antifreeze/water mixture (usually 50% antifreeze to 50% water). Hopefully the old coolant is your only problem. After you have it flushed, keep an eye on the antifreeze condition. If you have an automatic transmission where the radiator cools both the coolant and the transmission fluid, the transmission fluid could be leaking into the radiator. Some vehicles may also have an integrated engine oil cooler located in the radiator, but designed to keep the oil separate from the coolant (like transmission oil coolers). If the radiator reservoirs do not keep these fluids separate, oil could leak into the coolant. One last thing, oil in the coolant could also be an indicator of a cracked head gasket or other gasket that is leaking oil into the cooling system. Check the engine oil and transmission oil to make sure you don't have coolant mixing with these fluids.

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Electric Radiator Fan

Q: Do all cars have a belt that turns the coolant fan?

A: No. Many fans are driven by an electric motor. Most new passenger cars use an electric fan because it is more efficient and more suitable for front-wheel drive vehicles. Use caution when working on a vehicle with an electric fan. Electric fans can start without the engine running. Keep your fingers away from the fan area. If you need to work near an electric fan, disconnect your car's negative battery cable.

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Engine Block Cracked

Q: What would cause an engine block to crack?

A: A block can crack if the coolant (antifreeze and water mixture) freezes. An engine block has many coolant passageways. If the coolant does not have the correct antifreeze to water mixture, then the coolant is more susceptible to freezing. Coolant that freezes expands. If the force from the freezing coolant inside the engine is great enough, then the block could crack. Use an antifreeze tester to determine whether you have the correct mixture. For most climates, a mixture of 50% water and 50% antifreeze is the best. This mixture will not freeze even at -35 degrees.

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Frozen Engine Block

Q: My radiator has a small pin-hole leak. I was planning on getting it fixed here really soon. In the meantime, I used water to fill it up. This morning my radiator was frozen. Not knowing it, I started the car to warm it up to go to school. About 10 minutes later I went outside and the windshield wasn't unthawed. When I got in the car the temp gauge was all the way up. I immediately turned the car off and waited for about 15 minutes. When I tried to start the car again, it wouldn't start. I noticed that one of the soft plugs popped out of the engine block. What can I do?

A: The first thing you need to do is park the car in a heated garage to let the engine and radiator unthaw. From there, you will need to complete diagnostic work to figure out if the block, head, or radiator has cracked. I suspect that you possibly cracked a head or blew a head gasket from overheating engine. When the engine and radiator were frozen the coolant was not circulating. That is also the reason your windshield wasn't unthawed. The coolant did not circulate to the heater core.

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Heater Core Leak - Sweet Smell

Q: There is a sweet smell in my car coming from the air vents. Is this something I should be concerned about?

A: This sweet smell is probably an indication of a leaky heater core. The heater core is like a little radiator. It is mounted between the engine compartment and the passenger compartment. The heater core is used to transfer heat to the inside of the vehicle when you turn on the heater blower. If it is leaking, it drips in the heater ducts and sometimes on the floor inside the car. When the blower is turned on, the odor circulates inside the passenger compartment. Check to see if your coolant level is low. Do not open a hot radiator cap. If your coolant gets excessively low, you run the risk of overheating your car's engine and causing internal damage. If your coolant level is low, have your local service center perform a cooling system pressure test to find the leak.

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Heater Core Leak - Windshield Residue

Q: After a few minutes of turning on my heater an odor emits in my car. The windshield also appears to have a residue on the inside. What could be causing this?

A: The heater core may have a small leak. The heater core is a like a small radiator, commonly between the engine and passenger cabin. The heater core radiates thermal energy in the heating/air conditioning ducts of the car. Antifreeze flows through the heater core. When the blower fan is turned on, if the heater core is leaking, it will emit an antifreeze smell in the car. It could also be blowing some of that moisture onto your windshield. Check the floorboards for moisture and the antifreeze level in the coolant expansion tank. Only check the antifreeze when the engine is cold. A small leak in the heater core can emit a big odor.

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No Heat Inside

Q: My car never seems to warm up inside. When I turn on the heater I get plenty of airflow but the air is lukewarm at best. What do I need to do to get hot air in my car?

A: Your problem may be the car's thermostat. The thermostat controls the circulation of coolant in the engine. If the thermostat is stuck open, the coolant never gets a chance to warm up to the optimal temperature (usually 180 to 195 degrees Fahrenheit). And since the coolant is used to heat the inside of your car by flowing through the heater core, you only get warm air through the air vents. Also, check to make sure your engine is not low on coolant. If the coolant is low in the engine, air pockets can form. This can lead to a loss of heat in the passenger cabin. A clogged heater core can also cause heater problems. Follow the manufacturer's recommendations for coolant flushes to avoid crud being built up in the coolant system. Inoperative heater control valves are also potential problems in getting heat inside the car.

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Q: My car sometimes overheats when in traffic. I also hear a loud fan or belt noise. What's going on?

A: When moving down the highway air is forced through your car's radiator to help cool the engine. Your radiator fan is also designed to draw air through the radiator to assist in this cooling process, especially at slow speeds or when stopped. Depending on your vehicle, you either have an electrical fan or one that is mechanically belt driven. If you are hearing a belt noise, check the belt tension. Do this by pushing down on the belt between two pulleys when the engine is off. You should only have about a half inch of deflection (movement) for each foot of length between two pulleys. If you have more deflection than this, the belt may be loose and slipping. Also inspect the belt to see if it is cracked, glazed, torn, or if pieces are missing. A slipping belt can also cause the water pump not to circulate the coolant efficiently. If your vehicle has an electric fan, the sensor that sends the signal to run the fan or the electric motor itself may be faulty. Remember to always work on an engine when it is off and that an electric fan can start at any time even when the key is off. Disconnect the negative battery cable for safety.

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Radiator Cap Function

Q: What are the symptoms of a bad radiator cap?

A: A radiator cap has several functions. (1) It keeps the cooling system sealed from outside contaminants. (2) By keeping pressure on the cooling system, it raises the boiling point. (3) The radiator cap allows coolant to go to the expansion recovery tank when coolant gets hot, expands, and pressures increase. (4) As the system cools down, it allows coolant to return to the engine from the expansion recovery tank. A bad radiator cap can cause the engine to overheat at lower temperatures. This will cause the coolant to boil over to the expansion tank. A radiator cap that is faulty could also prevent coolant from returning to the engine. This would create a vacuum and cause the radiator hoses to collapse.

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Radiator Cap Pressure

Q: My car was overheating so I changed the thermostat. It is still overheating. The electric fan seems to be engaging and the antifreeze is full. What else should I check?

A: A bad radiator pressure cap could be causing the car to overheat. By keeping pressure on the cooling system, the pressure cap increases the boiling point of the antifreeze. If the pressure cap is not working properly, the engine could overheat.

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Radiator Hose Collapse

Q: What would make a radiator hose to collapse?

A: Radiator hoses commonly have a reinforcing spring inside that helps prevent radiator hoses from collapsing. If this reinforcing spring is faulty or missing, the hose may collapse when there is a vacuum in the cooling system. Another cause could be a faulty radiator cap. A radiator cap works to maintain a constant pressure in the cooling system. As the antifreeze mixture begins to cool after engine shutdown, a vacuum is created. If the pressure cap doesn't equalize this pressure, a radiator hose can collapse. The small vacuum valve in the radiator cap may not be working properly.

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Radiator Leak

Q: Would it be alright to put dish detergent in a radiator to find a leak by having the bubbles come out?

A: This is not recommended. Commonly two methods are used: an ultraviolet light detection system or a pressure tester. An ultraviolet (UV) light system uses a dye that is put into the cooling system. Once the coolant has circulated, then a UV light is used to locate the leak. The leak will glow under the UV light. Another method to use is a cooling system pressure tester. A pressure tester adds pressure to the cooling system pushing out the coolant at the leak.

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Q: What does the thermostat do in an engine?

A: The thermostat is the brain of the cooling system. It senses and controls the temperature of the coolant. When an engine is cold, the thermostat is closed. This keeps the coolant from circulating to the radiator, allowing the engine to warm up to the most efficient operating temperature. Once the engine temperature reaches the thermostat rating, the thermostat opens. When the thermostat opens, the coolant flows to the radiator where it releases heat and circulates back to the engine.

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Thermostat Stuck Closed

Q: The thermostat in my car gets stuck closed and my car overheats. What causes this and how can I fix it?

A: A thermostat is a maintenance item that periodically needs replacing. The open and control mechanism can wear out. The thermostat consists of a spring, wax pellet, a piston, and other components that can fail. I would recommend having the thermostat replaced and the cooling system flushed. There could also be particles in the coolant affecting the operation of the thermostat. Make sure you replace the coolant mixture with 50% antifreeze and 50% water. A 50/50 mixture will give the coolant a freeze point of -34 degrees Fahrenheit and a boiling point of 226 degrees Fahrenheit.

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Water Pump "Weep" Hole

Q: My car is dripping antifreeze around the water pump. What is the problem?

A: Water pumps have a built in "weep" hole. This is a spot that is built into the water pump that signals the car owner when the water pump's internal seals have failed. When the water pump is leaking from this hole it is time for replacement.

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White Smoke

Q: I have white smoke coming from the tailpipe on my car, what might be the problem?

A: Be aware that all cars, new ones included, may release a little white vapor when cold. This is caused from condensation in a car's exhaust system. Water dripping from the tailpipe is also fairly common from condensation. However if your car billows out white smoke after it is warm, you may have a problem. White smoke indicates that the engine is burning coolant. This means that coolant is getting into the cylinders and burning with the air-fuel mixture. Another indication of burning coolant would be a low coolant level in the radiator or overflow bottle. A blown head gasket, cracked block, or cracked head can cause coolant to leak into the cylinders. To prevent severe engine damage, do not continue to drive your car. Have a technician look into the problem.

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