My Honda Civic will warm up to normal operating temps if it's just sitting at idle. The minute I start driving around the temp gauge will slowly drop and eventually drop all the way back to C. It will also climb back up slowly to normal temp if I sit at a light. It has a brand new water pump from napa and a brand new radiator I just put in today since the old radiator started to leak.

This has been an ongoing issue since I put in the new water pump about a month ago and even with the new radiator. Cooling system has been bled each time. Only thing I can think of next is the thermostat. Any suggestions? The oil looks fine just in case people think it's a blown headgasket.

 

sounds like thermostat to me.

 

Check that. It's weird your car is getting too cold! The fans may be very effective and just kicking on too soon. That or check your connection for the ECT or whatever controls the dash temp. It could be bad and have something to do with an improper reading.

 

Yes it is weird. I'm hoping it's just the thermostat. Everything was working fine before replacing the stupid water pump.

 

Maybe something got knocked loose and clocked the thermostat. It's possible. I'm not sure if the temp sensor for the cluster can get clogged. It's always possible.

 

The only thing that was near the thermostat that I touched was the lower radiator hose. Besides that nothing was taken off from that side of the car. I'm sure if anything was clogged it would either overheat or just read cold all the time. I'll be getting a new thermostat today "Kicking myself for not buying one yesterday when I bought the radiator" but I should know by tonight.

 

my car was the same, it got to the point during the winter it would never fully warm up my entire 20mile commute. or go up then slowly go down.

 

It was the thermostat. Put in a new one and everything is back to normal. Thanks for all the replies and suggestions.

 

There was probably some material in the water pump that got stuck in the thermostat when you replaced it.

 

The thermostat looked normal with nothing stuck on it so it might of just been too old. A lot of **** on this car is still from the factory so it wouldn't surprise me

 

Yup. I run into that a lot on my car too. Vacuum lines that are OEM just fall apart when I go to unplug them. Congrats though. It's always good to see someone solve their problem.