Soooo a while back, my coolant temperature gauge wouldnt reach the middle at times, especially when it was cold outside. I replaced the thermostat, and had the same problem, maybe a little worse. So fast forward to now, I just did the timing belt and the kit from blau parts. Replaced the thermostat again (spring facing towards the inside of the water pump, o-ring between the thermostat and the flange), and the coolant, also a new radiator because my old one was leaking. I would estimate my coolant mixture is about 50/50. Anyway, it was about 56 degrees F last night, and my coolant gauge would only reach the first line on the freeway. If I let the car sit, and shut it off for a while, then turned it back on, it would reach in between the middle mark and next coldest mark, but once I started to move it would start to fall. The gauge seems to be a lot more dynamic than it used to be (it moves at different temp ranges at different speeds), before it would just hold at the middle and that was that. Im worried it wont reach warm enough temp for heat or efficiency once it gets colder outside. Any help would be great thanks.

 

Did you test the thermostat before installing it?

Drop it in boiling water and see if it opens. Sometimes they are doa

 

If it was stuck closed and wouldnt open shouldnt my coolant get too hot and not too cold?

 

coolant temp sensor? warm the car up so it gets to the max that the gauge will go, put a thermometer in the coolant reservoir and see what you get.

 

I replaced the coolant temp sensor, and cleaned the contacts about six months ago when I had to do the flange. And tonight, I left the car off for about 10 min, came back and started it, and it was dead center, then it dropped off as I started moving.

 

He is saying maybe the Tstat is stuck open. Where did you buy the Tstat from? usually just pony up and get one from the dealership. Never had a problem with the ones from there.

If you feel that the Temp sensor is good, it must be the Tstat IMO. How's the heat in the car, does it blow hot?

 

Ended up being the coolant sensor. I replaced it with one from ECS, the one I had in there was from NAPA and it definitely didnt last long at all, maybe it was never working right I cant remember.