how do you know when you need a new thermostat

 

thats kinda tricky, cause if it goes bad it will either get stuck "open" or "closed" if it gets stuck closed the car will run hot.

 

2000 M/C LS
I assumed it was stuck open because the water temperature. The temp gauge would never get hotter than 140 (approximate) and it fluxuated a little (10 degrees) and the car heater was blowing warmish--definitely not hot air. I think a good idea is to buy an extra thick and soft gasket ring ($4) to replace the gasket coming with the new thermostat. I fixed the small coolant leak on the front driverside intake manfold BOLT that was finger tight right next to the coolant temp sensor. I replaced the coolant sensor first and still had a leak draining to the coolant sensor. AAHHH the darn bolt was loose. No more VISUAL LEAKS AND STII MISSING FLUID COOLANT.......Gotta check out the intake gask thx to guys!!! Seriously thank you a ton and I dread the day I ever pay my local chevy dealer $140 an hour labor.

 

I just replaced my thermostat (stuck closed) and temp sensor because the gauge was dead and the CHECK ENGINE light came on. Ended up having to disconnect the battery for a couple minutes to reset the computer in order to get the check engine light to go out and the gauge working again.

And for you guys who say this is an easy job, try changing one on a small block...now THAT'S easy.

 

I read all the replies here and none really tell the whole story.
I need to replace Thermo on 2000 LS, looks like the throttle body has to come off to even get to the thermostat. I was unable to get throttle body out can someone help me out here plz. I can't figure out what I missed. Thanks.

 

if you have the 3.4 engine, i believe you're going to have to remove the crossover pipe to get to the housing

 

Carefully remove the throttle body air inlet duct.
Partially drain the cooling system.
Disconnect the radiator hose from the thermostat housing.
Remove the exhaust crossover pipe.

 

Even though changing a thermostat is easy, its always good to get a refresher on "how to do it". Thanks Kweef!!!!