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 4 2005, 11:51 PM Post #2
LS1 Inside! / Toolbox / Mechanical Engineer Group: Advanced Members Posts: 2,215 Joined: 5-February 04 From: NJ Member No.: 179	QUOTE (Glenn98ZM6 @ Feb 4 2005, 04:51 PM) you need water in the block that can get heated and that water will conduct the heat to the thermostat. if you don't do this, your relying on air to transfer the heat to the thremostat. not a good conductor of heat. I knew this was the problem, I was just concerned about getting the heads too hot before the thermostat opened. I went home, and my buddy (mechanic) stopped by just to check it out. Started it up, let it come up to 100+, then gave it a fast idle (2k rpm) with a couple of blips. I was watching the gauges, it went up to 180, then 195, then 210, then I was watching him, feeling the hoses. Then he goes check the gauge now, and it had dropped from 210 to 180. Bam---I'm done! I was also putting an IR temp gun on the t-stat housing. I saw it go upto 150 when the heads were at 180ish, then 155, 156....160, bam, the t-stat open. I was so close last night after I had slowly added coolant, cooled, added coolant cooled. I'm happy now. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/biggrin.gif) I'll let it cool overnight and check the levels again in the morning. Next step, align my front end (U/L CA's), mount hawker, install lexan. 2005 season is almost here and I'm still on schedule. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/2thumbs.gif) Thanks guys for the suggestions! (IMG:http://www.frrax.com/rrforum/style_emoticons/default/beerchug.gif)