Why is your car overheating and find out how to quickly fix it!

When your car overheats, your engine losses power and if not stopped sooner, you could lose the engine. Knowing the causes of car overheating can help you diagnose and fix it!

One the most common cause of car overheating is caused by a faulty thermostat. It could be stuck closed which prevents the coolant or the anti freeze from circulating in the engine. Anybody can test this quickly by running your hands around the top radiator hose.

If after starting the engine and getting it warmed up, that hose should be hot to touch otherwise, the thermostat is stuck closed. (Stuck open thermostat is where your engine will not warm up especially during the winter months). If the thermostat is stuck closed, the only solution is to replace it by using the right temperature application.

TIP on buying thermostat

There is a summer thermostat which is set to open at 180 degrees Fahrenheit and a winter thermostat which is set at 195 degrees Fahrenheit. Make sure you specify this when buying and you can also see it stamped on the thermostat probe end.

If your cooling system is leaking externally, the engine can lose the coolant resulting in car overheating. If you leave your car overnight and if you see coolant fluids under the engine, that is a good indication to find if your car has external leak.

A coolant pressure tester can be installed in the radiator cap hole and pressurized the cooling system to about 15 pounds of pressure. If there is a leak in the hoses or gaskets, you should see the coolant coming out.

Tip on external coolant leak

During the coolant pressure testing, if you find a small coolant leak especially on the radiator tanks (the solid housings between the radiator fins); get hold of a coolant liquid sealer. This sealer is usually bottled in small quantity (smaller than your pop soda cans) and it looks like black jelly beans inside.

It cost usually under $5 and can be stored in your glove box. When poured to the radiator cap opening, it is very effective in sealing small coolant leak even for a cracked side of the engine block. Just make sure you do the proper repair later. (Make sure also that the engine is cooled down before pouring the liquid kit).


This coolant sealer is not a permanent fix for car overheating. This is a patch repair only but have the radiator serviced as soon as you get it safe home (or still bring it to your garage).

Wiring color symbols

If the engine water pump has failed to work, that can also cause the car engine to overheat. You can run your fingers around the water pump housing and if the pump is leaking, you should see some oil or wetness in your fingers. For your safety, make sure to do this when the engine is stopped and cold.

If the fan hub or electric cooling fan is not working, the radiator will not be cooled and result in car overheats. Make sure you are familiar with all the cooling fan circuit like the engine cooling sensor, relay and whatever switches is used to activate the cooling fan.

TIP for checking the cooling fan

As soon as your engine reaches the maximum operating temperature, you should see the cooling fan activated or rotating fast. If not, then the cooling fan circuit must be checked. You can actually access the 2 cooling fan wires from the cooling fan motor at the back of the radiator and put direct battery power into them. If it works, then it means you have to check the rest of the coolant wiring circuit.

A bad radiator caused by dirty fins or clogged internal passages can also render your radiator useless. Over time, your coolant also wears out and where do you think all the coolant dirt and debris are deposited? Yes, it accumulates in your radiator. A regular radiator flushing and cleaning of the radiator is normal maintenance practice to prevent this.

Finally, the engine also wears out and that includes your cylinder gasket. This cylinder gasket is the seal between the coolant and your hot combustion chamber. Once that gasket is worn, the coolant will be sucked in to the combustion chamber and guess what? The engine will also overheat.

TIP on testing cylinder head gasket

A lot of garages can test your radiator for presence of combustible gas. For a fee, a probe tester can be put in the radiator cap hole to test this which can be done in minutes. Make sure to ask your local garage to do this if you suspect that your engine cylinder gasket is going.

If you experience any of these above car overheating symptoms, please contact your nearest radiator shop so you can avoid damaging your vehicle engine.

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