Hi,

I have recently noticed my temperature gauge bottoming right out during flat our downhill highway driving. The temperature is normal in city driving and uphill highway driving.

Would this be caused by the mechanical thermostat not closing properly? To what extent is the thermostat supposed to regulate engine temperature when drivng?

Can running at such a low temp damage the engine?

Cheers

 

Sounds like the therostat! My Integra did the same thing years ago. It was during winter and I didn't have any heat going downhill

 

Your problem may lie with a faulty guage sender (the one wire sender connected to engine block that goes to the dashboard temperature guage), a loose connector, or a faulty temperature guage.

If your car is already warmed up and the needle goes down (needle even bottoming out) during downhill driving, most likely your car is not running colder.

 

The fact that it occurs only when the engine is not heavily loaded and there is a very high airflow rate through the radiator (highway)) would suggest that it is unlikely to be an intermittent fault. I will replace the thermo and c what happens