ok so i just bought the car and im having this lil problem i got the car and the thermostat guage didnt work so i replaced the cooling temp sending unit the lil 1 wire one and the guage started working and now iv noticed that the car stays cool when driving it but when u come to some lights the car starts to get hot now i unplugged the rad fan thermostat switch and jumped the plug and the fans kick on so i figured the sensor was just bad so i replaced it still having the same issue the fan do cut on its just by then its almost 3/4 of the way up on the temp guage im rackin my brain and i have nothing unless one of the 2 sensors i have replaced new is bad the rad switch or the temp guage sending unit

 

I'm guessing you have a thermostat problem, and it sounds like it's not opening properly or as much as it should. It doesn't matter when the fans turn on if there isn't enough coolant flow through the thermostat to remove the heat with the radiator. The fact that the guage reads correctly when the car is moving tells me that the gauge (and coolant temp sender) are working properly, and you've also replaced the fan switch. So it sounds like the fans are probably working properly but there isn't enough coolant flow to the radiator to remove enough heat when the car is not moving.

Thermostats are cheap and easy, and it isn't a bad thing to replace simply for peace of mind.

 

yeah im actually a tech at a gmc dealership when i get to work mon im going to throw one in it and see how it goes

 

so i replaced the thermostat and its still doin the same thing so i took my laser temp gun and let it sit in my bay and get the guage go up and right before the rad fan cut on the upper rad hose was at 199 deg wich is what its supposed to be so im guessing it has to be a bad temp guaage in the cluster idk what does anyone else think

 

any ideas ?

 

Might have a ground problem or a corrosion problem with the wire going to the gauge. Either one can change the signal reference and make the gauge read high.

So the thermostat seems like it's working properly?

 

yes the thermostat is working fine just the guage goes like 3/4 of the way up before the rad fan kicks on

 

u could have air pockets in the rad/coolant lines take the rad. cap off and start the car and it will flush out the air pockets

 

what this man said, same thing happened to my civic like 3 times before i realized i was forgetting to bleed the system

 

well when i changed the thermostat i have a funnel that attaches to the rad and i let it rund for like 20 min in my bay and it seemed like there were no air pockets left in it