Troubleshooting and Maintaining Your Car’s Cooling System
The cooling system in your car works to keep your engine from overheating, and that is a very important job. If your vehicle overheats, it can mean the death of your engine. In this guide, we’ll tell you how to troubleshoot and fix the cooling system—and when it’s time to call a technician.
Why Is My Car Blowing Its Top?
If steam starts coming from under the hood of your car, turn off the air conditioner, open your windows, and turn your heater on wide open. This will help draw some heat from your engine—though unfortunately it will draw it into your car. You do not want your vehicle to overheat, so if a service station isn’t in sight and the other measures didn’t work, you need to pull over and shut off the engine immediately.
Here are some reasons your car may get hot:
- Leak in your cooling system
- Thermostat problem
- Fan belt is loose
- Water pump problem
- Low oil level
- Bad hose
- Dirty radiator plugged with debris
- Timing needs adjusting
- Needs coolant
Checking and Adding Coolant
Regularly checking fluids is a good plan for your wallet and for your safety. Let’s begin by learning how to take off the radiator cap. Never try to remove a radiator cap when the engine is hot. You will want to wait at least 20 to 25 minutes so that your engine can cool off. Observe safety rules (pull back long flowing hair, take off dangling jewelry, etc.) when working under the hood. Keep your cell phone handy to dial a relative and maybe your auto club or technician to let them know what is going on.
After the engine has cooled, remove the radiator cap by following these steps:
- Some cars have safety caps that after being popped allow pressure to escape. If you have a safety cap, very carefully pop it now. Step back while the steam escapes and then go back and twist the cap in a counterclockwise motion. If you don’t have a safety cap, use an old tee-shirt or a rag and place it over the cap before you turn. This will keep your hands from getting burned.
- After turning the cap, if things have not settled down—that is, if there is a lot of hissing and steam or coolant escaping—righty-tighty the cap back on. You’ll need to wait for the engine to cool more.
- When it’s safe to take the top off, twist in a counterclockwise motion and open the cap away from your body.
The radiator cap is pressurized.
Now check how much coolant you have, and the quality of it. There are two ways to do it, depending on the age of your car.
Cars Built After 1970
Most vehicles built since the 1970s have a coolant recovery or expansion tank. The tank should be made of a translucent plastic through which you can see the coolant level. There should be markings on the side that indicate hot and cold level. See where the coolant level lies in relation to these marks.
- If the engine is cool, you can add coolant by removing the pressure cap and bringing the level up to the cold mark.
- If the engine is hot, you will have to wait for it to cool down before removing the pressure cap to add coolant, since cold coolant and hot metal do not always agree with one another.
For a coolant recovery tank, you simply flip the cap to open it since it is not pressurized.
If you find either the expansion tank or the coolant recovery tank completely empty, there is a good chance the coolant level is low in the radiator, too. If you have a cap on the radiator, remove it when the engine is cool and top off the radiator before filling the expansion tank or the coolant recovery tank.
The coolant reservoir generally has “high” and “low” markings for an easy way of checking the coolant level. However, if you need to remove the cap, always wait until the engine cools.
Cars Built Before 1970
If you have an older car or one without either an expansion tank or a coolant recovery tank, you must check the coolant level at the radiator. When the engine is cool, remove the radiator cap and look into the neck; you should see coolant about ¾ of an inch below the top of the tank or the bottom of the neck. The coolant should easily cover the ends of the tubes. If the level is low, you will need to add some coolant.
It’s important to match whatever coolant is being used in order to preserve its protection qualities. Always follow the guidelines in your owner’s manual. You can purchase premixed coolant or you can purchase antifreeze that must be mixed with equal parts of distilled water. Add the coolant to the radiator to bring the level up to where it should be.
Flushing Your Vehicle’s System
Flushing the radiator helps keep the cooling system clean of rust and settling debris. The maintenance schedule in your owner’s manual will tell you when you should have your cooling system flushed and refilled. The most common service interval recommendations are every 24 to 36 months or 24,000 to 36,000 miles, but many later-model vehicles now have coolant that is designed to last 100,000 miles.
Given the environmental concerns alone, flushing a cooling system is a service that is best left to the professionals.
Checking and Replacing a Thermostat
Here are a few things to check before deciding to replace your thermostat:
- coolant level
- drive-belt tension
- temperature gauge operation (by putting a thermostat on the radiator)
An engine that seems to be taking longer to warm up, or is running cooler than normal per your temperature gauge, may indicate the thermostat is stuck open. If that is the case, you will need a new thermostat.
Here’s how to check your thermostat:
- Remove the thermostat
- Place it in a pan of water
- Heat the water slowly and observe the operation of the spring and valve as the water reaches about 200°F.
- The thermostat valve should open gradually. If you’ve taken the thermostat out of a cold engine and it’s already open, you can pretty much assume you need a new one.
Most thermostats are located under a metal housing (usually called a “goose neck”) at the upper radiator hose connection to the engine, but some import models may have them elsewhere. In all cases they are relatively easy to reach and replace, since they are designed to be serviced periodically. Any good vehicle-specific service manual sold at a parts store should show you this location on your particular vehicle.
Your vehicle’s thermostat is located between the engine and the radiator.
If you find you need a new thermostat, it’s a good idea to go ahead and have your technician flush and clean your cooling system at the same time. Why? Because you will have to drain a certain amount of coolant when you replace the thermostat, so if it’s almost time for this maintenance (coolant change), you might as well go ahead and have it done when you change the thermostat. Radiator hoses and the radiator pressure cap should also be checked for wear and rust.
Removal and replacement of the thermostat typically involves the following (check a vehicle-specific repair manual to see if there are any departures from the following procedure):
- Park your car on level ground. (When working under the hood and with toxic chemicals, remember all safety ruleswear safety goggles and gloves.)
- Drain the cooling system. Unscrew the thermostat housing and connecting water hose.
- If you are only replacing the thermostat, drain just enough of the coolant to a level slightly below that of the thermostat housing. If your coolant is less than a year old, drain it into a clean container and reuse it when the thermostat is reinstalled. If you see draining the coolant as problematic or are uncomfortable working around this toxic fluid, leave this repair for your technician.
- Note the location and placement of your thermostat so you can set the new thermostat back in place.
- Check for corrosion or old glue from thermostat housing and remove. Carefully clean the thermostat housing and all mating surfaces of any old gasket material to avoid leaks.
- Put the new thermostat in place, put on new gasket, and replace housing. Some vehicles will require that any air be bled out of the cooling system once it’s refilled. Again, check a vehicle-specific service manual for this procedure.
- Everything is back in place now, so you can check your work by running the engine for a while and check for leaks.
- Go for a drive and make sure the temperature gauge stays at full operating temperature (check your owner’s manual).
- Check for coolant leaks again, and your job is done!
Usually if you do routine maintenance, you can prevent overheating by checking the level of liquid in the system and maintaining it properly. If the cooling system is not maintained properly you run the risk of overheating, which can mean heavy repair bills that won’t guarantee the car won’t overheat again. The best advice is to keep the cooling system in good repair. Keep an eye on the coolant level and have your technician keep an eye on the entire system, doing maintenance as needed.
Following these simple maintenance and troubleshooting tips will keep your car’s cooling system running like a champ, no matter how hot it gets. Happy driving!
From The Complete Idiot’s Guide to Auto Repair by Vyvyan Lynn with Tony Molla
