Yep - I changed the thermostat and it is fixed now. The old one wasn't 'stuck' open, but I held it in front of a heater, and it opened pretty fast (a lot sooner than it should have). The check engine light was gone within a day.

 

You didn't have to clear the codes? And you didn't have to change your Coolant Temperature sensor?

 

Yea, in my original post I said that I changed that first but it didn't help anything. As far as the code goes, I didn't have to clear it. The light stayed on the 1st night but the 2nd day the light was gone. I think they are 'smart' enough to know when a problem is fixed. Hopefully, anyhow. It's been almost a week now and still no code/light, fans haven't been on when they shouldn't be and temp gauge is working fine. Oh, and the heater is a little warmer, too.

 

Then maybe the issue isJUST the Thermostat and not a combination of both the Thermostat and the Coolant Temperature Sensor.

Oh well, if you take off the thermostat housing to get to the thermostat, might as well replace the sensor anyways since it gives you more room to work with.

Sounds like all of our Montes are having no more issues with this anymore.

Whew!

But now I seem to have a new issue. My thermostat housing is leaking. This is ticking me off. I know there isn't a gasket that goes on the housing...just around the thermostat.

Now...do you put the o-ring into the seat of the block first...then put the thermostat on top of it? Or the other way around?

 

When I got my gasket, there was a little groove in the gasket that the thermostat fit into. The gasket and thermostat then slid into the block. It's kind of hard to explain, I hope you know what I mean [&:]

 

uhhhh....oops.

I didn't put it in the groove. I just put the o-ring in first, and set the thermostat on top of it.

Back to work!

 

Hahaha! Sorry to laugh at you, but you have to admit, that's pretty funny! Don't spill too much antifreeze! Good luck!

 

I had this exact problem with my 2001 monte carlo ss. I went and replaced the engine coolant sensor which is located in the front of the engine through the exaust manifold on the right side. It has an electical feed with two wires coming from it that plugs into the top of the sensor.It's not fun to get at but is capable with the correct ectensions, while i was in there i also replaced my upper and lower hoses and flushed the sysytem to find out that the guage was still acting up. When you turn the key to power, the guage moves just a little bit up, but still wont work. My buddy mentioned to replace the thermostat which is located where the upper hose goes into the block on the top right side of the engine. Its a pain to work around all the wires, but with patience I got it done and it fixed the problem, my guage has not acted up once and that was about 4 months ago i did all of this now. The engine coolant sensor is about $10 and the thermostat is $7. Dont for get to get a new seal for that thermostat and if you replace the coolant sensor you will need high temp silocone! Good luck!

 

I just bought a 2001 Monte Carlo SS, I have had it for two weeks, and have a similar situation, and all of a sudden the check engine light comes on, and the temperature gauge isnt working. I dont know if it has any thing to do with the outside temperature, it has gone below freezing for the first time this season, Should I just replace the Thermostat, should that fix my problem?

 

Since it's pretty easy and inexpensive to replace both, I would replace both. That way you will know the problem is fixed.