Car problems that can cause the engine to overheat range from low coolant level to blown head gasket, bad water pump, faulty temperature sensor, and many other issues.
If your engine is overheating due to one of these problems, continuing to drive can lead to serious engine problems such as a blown head gasket or engine locking up. It is critical to take immediate action if your car is overheating to avoid causing expensive damage to the engine.
In this article, we go over the most common problems that cause a car engine to overheat and what you should do when you see the temperature gauge jump to the red.
Why does a car overheat?
A car engine can overheat for a number of reasons which we list below, but in most cases, it is due to low engine coolant level or because a component or sensor of the cooling system has failed. Once the cooling system fails and the coolant no longer moves through the engine and the engine can no longer be cooled down.
Common Problems that Cause Overheating
Common problems that cause a car engine to overheat include:
- Low coolant level or no engine coolant,
- Bad engine temperature sensor,
- Coolant leak,
- Loose radiator hose clamps or broken fitting,
- Bad water pump,
- Clogged radiator,
- Cracked radiator,
- A stuck thermostat in the closed position,
- Faulty cooling fan / viscous fan clutch,
- Bad coolant hose,
- Broken belt,
- Bad engine control unit (ECU),
- Blown fuse,
- Clogged or cracked heater core,
- Blown head gasket.
What To Do When Car Overheats
Let's take a look at what you should do when the engine overheats.
Turn off the engine and let it cool down
- Pullover immediately or as soon as it is safe to do so.
- Park the vehicle and turn off the engine.
- Allow the engine to cool down for at least 15 minutes.
- Pull the hood release and open the hood.
- Inspect engine, coolant hoses, radiator for leaks without touching any parts. Visibly checks the engine coolant level. Do not open the radiator cap when the engine is still hot.
- If the coolant level is low, allow the engine to cool down then add the recommended 50/50 mixed engine coolant.
Once the engine has cooled down completely, you can perform further checks and troubleshooting. It can take over an hour for the engine to cool down.
The first thing you need to check is the engine coolant level. Locate the engine coolant overflow reservoir and look at the side of it.
Most reservoirs are translucent and allow you to check the level. If the tank if black, wait for the engine to cool completely then remove the cap to check the level.
Next, start to visibly inspect the hoses, radiator, thermostat housing, water pump, or heater core.
Check Radiator & Hoses
Visibly inspect the radiator and hoses for leaks. Look for coolant on the ground and steam from the radiator cap.
Replace the radiator cap. The radiator cap has a spring that opens if there is too much pressure build-up, often this spring wears out and releases coolant.
Inspect if the engine belt is still in place or have come loose. A loose belt is not able to rotate the water pump pulley and can lead to engine overheating. Water pump moves the coolant through the cooling system.
Check engine oil color and level
Remove the dipstick and note the color of the engine oil. If you spot a white looking oil, there is a high chance you have a bad head gasket. This is indicated that the engine coolant got mixed with the oil.
If you have a white looking oil, it means the cylinder head gasket requires replacement, which is an expensive repair. We recommend that further troubleshooting be performed by a certified auto mechanic.
Check Radiator Fan
Start your engine up after not seeing any leakage and let it warm up. After a few minutes, the operation temperature should be reached. The Radiator Fan should start up and pull in the air across the radiator to help cool down the coolant in the cooling system.
A broken fan motor or a worn-out fan clutch can’t reduce the temperature. Check the fuse box for the radiator fan fuse/ relay. If those are in order, let the car cool down.
The Thermostat is a valve that lets the coolant pass through your cooling system and engine. When a thermostat stuck in the closed position, water is no longer able to move correctly, and the car overheats.
To check the thermostat, we have two options.
- The first option: Start up the car and let it idle for about 15 minutes. Carefully touch both coolant hoses from the radiator to the engine. When the thermostat works appropriately, they should both become warm. Do not allow the engine to overheat past the normal operating temperature.
- Second option: Remove thermostat housing and visibly inspect it. You should be able to move the thermostat valve. If the thermostat is stuck closed, the valve will not move.
If you remove the thermostat for testing, consider replacing it as the cost of a new engine thermostat is relatively low.
Add Engine Coolant
After all the leaks are fixed, and repairs are completed, add 50/50 engine coolant mixture as per the service manual.
- Fill up to full and turn the heating system to hot.
- Start the car without a radiator cap and let it warm up to operating temperature, about 15 minutes. The system will bleed out access air. In some cases, vehicles have a 2nd position were to bleed it out to make this process easier. This is vehicle specific; you may verify if this is an option for your car.
- Replace the radiator cap.
- After the air is out and the radiator fan turns on, and the engine coolant level is correct, close the cap, and go for a test ride.
- The temperature needle should stay in the middle of the gauge.
If the car still overheats and all procedures were followed properly, you may opt to get the vehicle checked at a local mechanic who can put pressure on the system to see if you have missed any leaks. Auto repair shops can measure if there are any exhaust gasses in your coolant system and test for a blown head gasket.
Possible problems that can cause a car to overheat range from a cooling hose leak, faulty cooling fan, broken water pump, or bad temperature sensor. When an engine overheats, it is either because the coolant is not cooling the engine or there is no coolant at all. If it is not obvious why your car is overheating, we recommended having a certified auto mechanic diagnose the problem. Regular visible inspection and maintenance can avoid a lot of headaches and expensive repair costs down the road. When adding engine coolant, always use the correct mix of engine coolant. Using the wrong mixture of engine coolant and water can cause the vehicle to overheat.
Frequently Asked Questions
How long does it take for a car to cool down after overheating?
It takes over 30 minutes for the car to cool down to normal operating temperature. In extremely hot weather it can take even longer. It takes about up to two hours to completely cool down.
Can I drive my car if the radiator coolant fan is not working?Not recommended. The following procedure may work in some cases. Do not drive if the engine continues to overheat.
- Immediately turn off your AC and roll down your windows
- Turn your heater to hot and fan to high. The heater core will pull out heat as much as possible.