So while i was taking out my engine(b18a1), i changed my thermostat and now my temp gauge doesn't go up when i drive. The temp gauge goes to normal operating temp when i just let my car idle for about 10 min or so (normal) but when i start driving it goes back down to cold. My radiator fan does turn on and everything else seems normal. Just my idle is a little high because i guess the it thinks its still cold. Do you guys think its my thermostat? It's weird cause it was a brand new one though.

 

Sounds normal unless there is air in the system.

 

If there was air in the system, wouldn't that cause the idle to be high?

Well i tested it again and when it's at idle, it warms up just fine. Fan turns on and everything. When i drove it, it was at normal operating temp but i watched the gauge as i drove and it went down slowly. i was driving it pretty hard too. my only guess is that i have a faulty thermostat?

 

If your not overheating it should be fine. While driving air is flowing through the radiator which cools the system. If your thermostat was bad it wouldn't open which would make your car overheat.

 

It could be open a little bit as well. I've noticed when i installed the new thermostat, the pin at the top of the stat was flipped around. not sure if that affects anything? i would guess that water is just constantly going through that small hole?