Is your car overheating then going back to normal? You can tell if your temperature gauge keeps going up and down between C and H.
This may be due to issues with your coolant level, thermostat, radiator, or water pump.
I’ll explain the causes in detail and give you tips on how you can fix it.
Low Coolant Level
Low coolant can cause your car to overheat under a heavy load and then go back to normal when the load decreases.
The first thing to do when your car keeps overheating and going back to normal is to check your coolant level. If it’s low, all you need to do is add more coolant into the reservoir until it reaches the “High” marking.
Be sure to do this when your engine is cold to avoid splashing hot coolant on your body.
A faulty thermostat might make your car overheat and then return to normal.
The thermostat is a device that stays shut when the engine is cold and then starts to open as the engine gets hotter.
If the thermostat fails, it might stay closed and restrict coolant flow to the radiator.
This restriction can lead to overheating. But, when the load reduces, the lack of coolant circulation might not be as critical. This would allow the engine to cool down temporarily.
The thermostat is located underneath the housing on the top of the engine. It’s usually connected to the hose going to the top part of the radiator.
Use a temperature gun to check the temperature on either side of the thermostat. If it’s shut, one side would have a high temperature while the other side would be cooler.
You can get a thermostat replacement for about $5 to $10 to fix the issue.
Air Pockets in the Coolant System
When air gets stuck in the coolant system, it makes pockets where coolant should flow. This messes up the engine’s cooling process, causing it to overheat when there’s a lot of strain on the engine.
But when the engine load decreases, the air pockets may shift, allowing the coolant to flow.
One way to know that you may have air pockets in your coolant system is that your heater would stop working. So if you turn on the heater and it’s not working properly, then you may have air pockets in your coolant.
To fix this, connect a jug to the coolant reservoir, fill it with coolant, and let the engine run. As the bubbles come out, and then cool, they’ll go in and bleed the whole system.
Radiator Cooling Fan Issues
The radiator fan helps dissipate heat by blowing air through the radiator. This cools the coolant circulating through the engine.
If the radiator fan is faulty, it won’t blow enough air, especially when the engine is hot and the car is not moving fast. This inadequate cooling can lead to overheating.
But when the car is in motion, there might be enough airflow to cool the engine temporarily.
Cooling fans only start to work when a vehicle is moving below 25 – 30 miles per hour. If the car is moving above 30 – 40 miles per hour, air will go past the radiator and cool the engine. In such situations, the engine would not need the fan.
If your engine gets too hot when you’re stopped at a red light, but cools down at 30-40 mph, your cooling fan may be faulty.
Failed Engine Coolant Temperature Sensor
The coolant temperature sensor keeps track of how hot the coolant is. This gets sent back to the engine control module.
If it fails, it will provide incorrect readings to the ECU. For example, it might show that the engine is cooler than it is. This can affect engine performance and potentially cause overheating.
When the engine isn’t working as hard, the wrong readings from the broken sensor may not be as bad, letting the engine cool down for a bit.
Blocked Coolant System
If every other thing on the list seems fine, the next thing to check for is a blockage in the coolant system.
If you have a build-up of debris in your coolant system, they’ll clog it up and prevent easy flow of coolant to the engine.
You can just drain the coolant and refill the reservoir with fresh coolant.
Failing Water Pump
The water pump pumps out the water through the cooling system. If the water pump keeps failing periodically, your car will overheat for a while and then go back to normal.
You can diagnose a failing water pump by checking to see if water drips from the seat pole.
The issues listed above would cause your car to over heat and then go back to normal. Most times, the problems are more pronounced when there’s heavy load on the engine.
In any case, ensure that you get the problem fixed as soon as possible to prevent a possible engine failure.
Ugo is a passionate car enthusiast with a Bachelor of Electrical and Electronics Engineering degree and hands-on experience in troubleshooting and fixing automobiles.
I combine my electrical and mechanical engineering knowledge with practical skills to address car-related issues.
My love for cars and dedication to educating others led to the creation of Fixandtroubleshoot.com!