Why Is my Car Thermostat Going up and down

Why Is my Car Thermostat Going up and down

You pull over by the roadside because you saw the overheating light coming on and the temperature gauge pegged up. Then you start the car a few minutes later and everything seems to be fine. Again, as soon as you start driving, the temperature goes from cool to hot within a minute. The thermostat keeps going up and down while you drive, and you suspect an issue with your thermostat or the car’s cooling system. If this instance seems to be similar to what happened with you, then must be curious to know why is my car thermostat going up and down. This OneHowTo.com article will talk about the issue in detail.

Air in the coolant system

If your car thermostat keeps going up and down, then there are chances that the cooling system has trapped air inside it. Some cars have a hard to burp cooling system, which need to be filled appropriately and also burped if there is an air pocket in its system. In that case, you may need to remove the block plug so that the coolant can flow out.

Head gasket issue

Air may get trapped in your cooling system due to a head gasket issue as well. Combustion gases may sometimes enter your car’s cooling system. There might be head gasket leakage into your coolant. Ask your mechanic to check for such leakage during your car’s cooling system pressure check.

Open the block plug so that the coolant can flow out.

Bad connection with the temperature sensor

If your car thermostat goes up and down, then chances are that there is a connection problem between the temperature sensor and the temperature display positioned inside your car. Its wire might have become loose, due to which you must be getting false indications. So, take your car to a mechanic and make sure that the wires are safe and intact.

Low coolant level

If the coolant level in your car has gone down, air may build up in the empty part, and cause an air pocket. Due to this, the air may get trapped inside and cause the thermostat to go up and down. So, check your coolant level at regular intervals of time, and make sure that it is maintained at the proper level.

Bad thermostat

You need to make sure that your car thermostat is working fine. Sometimes, the thermostat may get stuck at an all closing or all opening position. Start your car, press the auto button for climate control, and check that whether the radiator cooling fans are turning on or not. If they are on, then there might be some problem with the cluster temperature gauge. In that case, the issue can be resolved only by getting it replaced.

Issue with the heater control valve

The heater control valve might be closing and not allowing more hot fluid to enter once the inside core fluid has cooled down. The car should not lose heat if the engine has achieved its full temperature for operation. The hot fluid should constantly flow from engine to the car’s heater core. So, your core might be plugging up or there is some issue with your heat valve.

If you want to read similar articles to Why Is my Car Thermostat Going up and down, we recommend you visit our Car Maintenance and Repair category.