Anybody ever have a stuck thermostat (closed)? - F-Body Road Racing and Autocross Forums

Any of you guys ever have a thermostat stuck closed? I swapped mine a few weeks ago for a Evans hi-flo, 160 stat and topped the fluid off. I then started it last night, and was trying to get the air out, but the temp on my aftermarket gauge climbs to 200-210 rather quickly (<5 minutes). Every time I let it sit and cool, it takes a little bit of coolant. (Checked it at 5:15 this morning, probably took another pint). It seems that there is an air pocket so big that the thermostat doesn't open up yet.

Few notes:

1. The aftermarket gauge sensor is on the passenger's side head.

2. Stock gauge is on the driver's side head. Stock gauge shows ~210....of course, that's what it always says from 160-225!

3. Is there air or vapor making the aftermarket gauge show ~210, while the stock one is upto ~190 according to the Mastertech scanner? If it was at 195, the fans would kick on (LS1Edit). I've yet to hear the fans kick on while attempting to get more fluid in.

4. I always shut the car off when the aftermarket gauge shows ~210 in fear of doing damage.

5. I've taken the hose off at the top of the driver's side head, and coolant flows right out, no bubbles.

I guess when I get home I'm going to try starting it up again and see if it will open again? I just don't know how long to wait before I fear the heads are getting too hot from no circulation and/or air pockets. If that doesn't work, I'm going yank the thermostat and see if it is defective.

It's weird, last time when I had the waterpump and t-stat out for my cam install (~15k miles ago), I had virtually no problems adding coolant and purging air without even messing with the little hose coming off the heads.---But, I did have the front of the car on ramps, elevating it about 10" higher.--Was that enough to make the radiator neck the high point of the system, thus allowing the air out quickly?

Just don't want to overheat my motor/heads!! (IMG:http://www.frrax.com/rrforum/style_emoticons/default/banghead.gif)

Teutonic Speedra... Teutonic Speedracer View Member Profile	Feb 4 2005, 06:07 PM Post #1
LS1 Inside! / Toolbox / Mechanical Engineer Group: Advanced Members Posts: 2,215 Joined: 5-February 04 From: NJ Member No.: 179	Any of you guys ever have a thermostat stuck closed? I swapped mine a few weeks ago for a Evans hi-flo, 160 stat and topped the fluid off. I then started it last night, and was trying to get the air out, but the temp on my aftermarket gauge climbs to 200-210 rather quickly (<5 minutes). Every time I let it sit and cool, it takes a little bit of coolant. (Checked it at 5:15 this morning, probably took another pint). It seems that there is an air pocket so big that the thermostat doesn't open up yet. Few notes: 1. The aftermarket gauge sensor is on the passenger's side head. 2. Stock gauge is on the driver's side head. Stock gauge shows ~210....of course, that's what it always says from 160-225! 3. Is there air or vapor making the aftermarket gauge show ~210, while the stock one is upto ~190 according to the Mastertech scanner? If it was at 195, the fans would kick on (LS1Edit). I've yet to hear the fans kick on while attempting to get more fluid in. 4. I always shut the car off when the aftermarket gauge shows ~210 in fear of doing damage. 5. I've taken the hose off at the top of the driver's side head, and coolant flows right out, no bubbles. I guess when I get home I'm going to try starting it up again and see if it will open again? I just don't know how long to wait before I fear the heads are getting too hot from no circulation and/or air pockets. If that doesn't work, I'm going yank the thermostat and see if it is defective. It's weird, last time when I had the waterpump and t-stat out for my cam install (~15k miles ago), I had virtually no problems adding coolant and purging air without even messing with the little hose coming off the heads.---But, I did have the front of the car on ramps, elevating it about 10" higher.--Was that enough to make the radiator neck the high point of the system, thus allowing the air out quickly? Just don't want to overheat my motor/heads!! (IMG:http://www.frrax.com/rrforum/style_emoticons/default/banghead.gif)

Teutonic Speedra... Teutonic Speedracer View Member Profile	Feb 18 2005, 11:13 PM Post #2
LS1 Inside! / Toolbox / Mechanical Engineer Group: Advanced Members Posts: 2,215 Joined: 5-February 04 From: NJ Member No.: 179	OK. Update- I e-mailed Evans Cooling this morning describing the situation. They agreed, that it definitely sounds like a sticking thermostat, or one that is set at the wrong temp. They said it would be the first defective one, but it is possible. Their first response to the e-mail was that they were sending me a new one first thing Monday with a return label for me to send the other one back at MY convenience. I then decided to call them and Dave was very helpful. We talked a bit and a stuck thermostat made plenty of sense. He also talked a bit about the cooling system, and water pump in the LS1. It is uneven slightly, but he didn't try to sell me on their pump which is a bit pricey. He said he would suggest that when the stock pump goes, or if you are overhauling the motor. He also talked about how their thermostat has a better bypass operation helping the cooling. All in all, very helpful! (IMG:http://www.frrax.com/rrforum/style_emoticons/default/biggrin.gif) Two thumbs up for customer service! I didn't even request a new thermostat, they just said they would send one. I hope this one eliminates my problems. Then I can stop doing this..... (IMG:http://www.frrax.com/rrforum/style_emoticons/default/banghead.gif) (IMG:http://www.frrax.com/rrforum/style_emoticons/default/banghead.gif) (IMG:http://www.frrax.com/rrforum/style_emoticons/default/banghead.gif) ---When I have problems and they have anything to do with the motor, it bothers me until it's fixed. Unknowns are the worst.