Recently I have noticed my temp gauge rise when I am stopped or idling and also when I run the AC. However, it begins to fall back down once I start to drive. At first I thought it was the fan clutch which I recently installed 2 days ago. Unfortunately, the problem is still there. There are no leaks from neither the water pump nor the radiator and my radiator and reservoir and completely filled. Could this be the work of a thermostat stuck closed or what ? Please let me know.
My car has 180000 miles.
My car has an automatic transmission.
If you are getting overheating only at lower engine speeds with no obvious reasons, then you will need to check if there is good flow through the radiator using a laser temperature sensor. By doing this you will be able to see if there is any blockage in the radiator.
If the temperature is good in the radiator then you should check the operation of the water pump. If it is not pumping properly it should due to worn pump blades. Replace the water pump and recheck the system as necessary.
I’d suggest getting some help from a certified mechanic who can run these checks and diagnose your overheating issue firsthand. Good luck.