Stuck Thermostat?

DaRockwilder · 12-05-2007, 12:25 AM

Hey all!

I suspect that my thermostat is stuck open on my '03 Ecotec with about 104,000kms on it. I didn't really notice until it started to get cold out, and my car won't warm up. What happens is, when I let it run for about 10 minutes, I come back outside and its still ice cold, the temp gauge is only half way to the first line on the gauge. The coldest its been out when this happens is -20*C. When I drive the car it warms up, but if I park it and let it idle after driving it, the temp gauge falls back down. Normal operating temp for me is at half way on the gauge. I don't know what the lines represent. I pulled the relays for the cooling fans, and tried the heater on something other than defrost so the fans don't run, but I still have the same problem, even without the fans on.

When the motor is running, with the water temp well below 180*, there is no pressure in the radiator hoses, when I squeeze them, the coolant bubbles in the surge tank. I can only assume that if the thermostat was closed, there would be more pressure in the system.

Am I correct to assume the thermostat is stuck open? Is it located in the pipe on the back of the water pump on an ecotec?

Anyway, thats my story.
Thanks for anything!

01silveralero · 12-05-2007, 12:36 AM

it sounds like it is stuck open. the middle represents ~200 monitored scanner temp reading and gauge at same time

Redog · 12-05-2007, 02:01 AM

Are you losing coolant? Is your coolant tank full? Any SES lights? (I doubt that one)

Cliff8928 · 12-05-2007, 02:29 AM

My Ecotec NEVER gets to the middle of the gauge. And when it sits idle the heat is definitely not as hot. It's always been that way since new.

07gxpgray · 12-05-2007, 08:02 AM

sounds stuck open to me.

DaRockwilder · 12-05-2007, 09:31 AM

The surge tank could use a top up, but its maybe only 3/4" under the full cold mark. Its been like that for a long time though. I'd imagine the coolant hasn't been changed in the car, so I should probably do that. While i'm at it, I'll throw in a new thermostat. Kind of a pain though I think as i'll have to remove the exhaust manifold. oh well.

I read that the ecotec was designed to run at 195*, so thats probably what my gauge is saying.

nickbain · 12-05-2007, 09:42 AM

I got the same thing goin on. It just doesn't seem to throw as much heat as it should, like an hour and a half trip and the blower on high the whole way. Normally on any other vehicle after about 10-15mins I have to turn the heat down cause it's too hot. And you gotta remove the exhaust manifold????

maybe time for header?

DaRockwilder · 12-05-2007, 09:51 AM

Yeah, the thermostat is located at the back of the water pump, so with an automatic transmission, you have to pull the exhaust manifold to get at all the bolts in the water pump housing. If you have a 5-speed (which you sig says you do) you might be able to switch it out without removing anything, but I can't say for sure. Well you have to drain the coolant of course, or at least expect to replace a lot of it as it drains out of the pipe you disconnect.

Removing the exhaust manifold is no big deal, actually. The car should be new enough that everything should come apart fairly easily. I might need a new manifold to down pipe gasket, if there is one, and maybe the bolts for the down pipe, but the ones in the head should be a piece of cake. i think they might even be studs.

I even have an O2 sensor socket.

TheEdgeofSanity · 12-05-2007, 03:00 PM

what about on a 3400? mine's doing that...i let it sit for 10-15 minutes and it is barely off the cold line.

nickbain · 12-05-2007, 06:37 PM

Quote:

Originally Posted by TheEdgeofSanity

what about on a 3400? mine's doing that...i let it sit for 10-15 minutes and it is barely off the cold line.

For some reason with my old alero it was the same but when I started driving it warmed up fast and I had to turn down the heat within 2 mins or so of driving.

billytheman1188 · 12-05-2007, 06:48 PM

Quote:

Originally Posted by Cliff8928

My Ecotec NEVER gets to the middle of the gauge. And when it sits idle the heat is definitely not as hot. It's always been that way since new.

when it sits it doesnt go up any!? damn, ever since i got my LIM leak fixed, if i have the car sit too long when its all warmed up in hot weather, the needle goes past the half way mark...... i hate it!

DaRockwilder · 12-05-2007, 07:21 PM

Quote:

Originally Posted by TheEdgeofSanity

what about on a 3400? mine's doing that...i let it sit for 10-15 minutes and it is barely off the cold line.

3400 should be fairly easy to change. My haynes manual says its at the end of the lower intake manifold on the drivers side of the engine compartment. You follow the upper radiator hose until you find it. It'll be a metal pipe with two bolts holding it to the block.

nickbain · 12-05-2007, 08:19 PM

Quote:

Originally Posted by DaRockwilder

3400 should be fairly easy to change. My haynes manual says its at the end of the lower intake manifold on the drivers side of the engine compartment. You follow the upper radiator hose until you find it. It'll be a metal pipe with two bolts holding it to the block.

If I remember correctly you have to take the tb off to get at it, but that was almost 3 years ago when I did mine, I just changed it because I was doing the LIMG and everything was exposed. I don't know for sure if you gotta take off the tb but there was something in the road to make it a PITA I think.

TheEdgeofSanity · 12-05-2007, 08:37 PM

hmmm.....well, if my thermostat is stuck open, will it hurt anything? i can deal with it taking longer to warm up for the time being because i have nowhere warm to work on it right now.

billytheman1188 · 12-05-2007, 10:29 PM

Quote:

Originally Posted by TheEdgeofSanity

hmmm.....well, if my thermostat is stuck open, will it hurt anything? i can deal with it taking longer to warm up for the time being because i have nowhere warm to work on it right now.

Just put on a sweatshirt, a heavy coat, some warm pants and a nice warm hat.... you will be fine. It shouldnt take too long.

Cliff8928 · 12-06-2007, 02:35 AM

Quote:

Originally Posted by billytheman1188

when it sits it doesnt go up any!? damn, ever since i got my LIM leak fixed, if i have the car sit too long when its all warmed up in hot weather, the needle goes past the half way mark...... i hate it!

Actually, if I'm driving it and then let it sit, the temp usually goes down.

01silveralero · 12-06-2007, 04:19 AM

Quote:

Originally Posted by nickbain

I don't know for sure if you gotta take off the tb but there was something in the road to make it a PITA I think.

yes you could take the tb off. other people suggest take the exhaust heat shield off to get to that bottom bolt. if you have small hands it is kinda do-able without removing tb or heat shield. when you do the lim leak repair it is a good idea to do thermostat too

jackal2000 · 12-06-2007, 05:14 AM

Quote:

Originally Posted by 01silveralero

yes you could take the tb off. other people suggest take the exhaust heat shield off to get to that bottom bolt. if you have small hands it is kinda do-able without removing tb or heat shield. when you do the lim leak repair it is a good idea to do thermostat too

you realize this is the ecotec section right? not the 3400 section. all of what you just said does not apply.

nickbain · 12-06-2007, 08:47 AM

Quote:

Originally Posted by jackal2000

you realize this is the ecotec section right? not the 3400 section. all of what you just said does not apply.

Accually it kinda does because he quoted me and I was talking about the 3400 in response to theedgeofsanity's question about his 3400 and changing the t-stat in that, so while it is in the wrong section his post is relavent(sp?).