LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Temp gage pegged, then drops instantly

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Old 05-16-2003, 04:45 PM
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Temp gage pegged, then drops instantly

Ever since I did my cam swap (along with headers and CSI pump) I've been having cooling issues. The gage will very quickly jump all the way to 260 without warning, and then it goes back down almost instantly. Sometimes it stay for awhile, goes to 1/2 way, back up, back to normal then pegged again. It might do it one day and not do it again for days. I've bleed the system several times, and it still comes back. The overflow is full, pump is pumping water. When the gage is pegged u can open the bleeder screws and a crap-load of "air" comes out, I mean a bunch of it too! I've prob. bleed this thing 4 times now and it still keeps coming back. No water in oil, no anti-freeze smell out the tail pipes. The other day it was around 50-55 degrees out and it was steaming out the pipes, like a cold day but it didnt smell like coolant, Is it possible that I have a blown head gasket, that is just "weeping" every so often, or is that possible?
I did notice a small leak around the sensor in the w/p, could it be drawing air in the system due to the leak? It doesnt blow coolant out the rad. with the cap off, wouldnt it do that if the head gasket was blown? All replies welcome!
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Old 05-16-2003, 05:11 PM
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You definitly have to get all the air out.Try to do it with the front end raised to help the air out.Also possible your T- stat is sticking.
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Old 05-16-2003, 05:24 PM
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Re: Temp gage pegged, then drops instantly

Definitely sounds like a T-stat problem.
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Old 05-16-2003, 06:02 PM
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Re: Temp gage pegged, then drops instantly

Originally posted by kirschman
Ever since I did my cam swap (along with headers and CSI pump) I've been having cooling issues. The gage will very quickly jump all the way to 260 without warning, and then it goes back down almost instantly. Sometimes it stay for awhile, goes to 1/2 way, back up, back to normal then pegged again. It might do it one day and not do it again for days. I've bleed the system several times, and it still comes back. The overflow is full, pump is pumping water. When the gage is pegged u can open the bleeder screws and a crap-load of "air" comes out, I mean a bunch of it too! I've prob. bleed this thing 4 times now and it still keeps coming back. No water in oil, no anti-freeze smell out the tail pipes. The other day it was around 50-55 degrees out and it was steaming out the pipes, like a cold day but it didnt smell like coolant, Is it possible that I have a blown head gasket, that is just "weeping" every so often, or is that possible?
I did notice a small leak around the sensor in the w/p, could it be drawing air in the system due to the leak? It doesnt blow coolant out the rad. with the cap off, wouldnt it do that if the head gasket was blown? All replies welcome!

Does the engine run rougher. With steam comming out of the tail pipes, it kinda sounds like a burned/ blown head gasket. As far as the temp gauge , it could be melted and damaged because of the heat . If it gets too hot, the connector will melt, and could fall out of the head. Mine did this when I blew a head gasket . But my gauge did not go up and down. After it pegged, it went down and stopped because the connecter melted and fell out. So maybe yours could be melted or damaged, BUT still in the cylinder head. My car also drove terrible , because about 4 or 5 cylinder's had water in them.

I however DID have coolant in the oil, (mine blew bad) but I think you can blow a head gasket (depending on where it's blown) without getting coolant in the oil. Anyways If you don't have a blown head gasket yet , you probably will sooner or later if your car gets that hot so often.
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Old 05-16-2003, 09:23 PM
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Check the wiring on your coolant temp sensor in the drivers side head. Sounds like you may have a burnt sensor wire. If you burn through the insulation and it rests on the header it will peg the top of the range.
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Old 05-16-2003, 09:32 PM
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sounds like your CSI might be having some problems. does the car actually get hot? i mean if you pop the hood can you hear the coolant boiling in the heads? my CSI pump had a bad connection in the fuse box when i wired it up and got really hot a couple time... pushing down on the relay i got it going again and finally i think fixed if for good. but when it was hot i could hear the coolant boiling and the pump made no sound. im betting on either busted sensor from the header install or more likely a bad connection to the water pump.
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Old 05-17-2003, 04:06 PM
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All the wiring is ok. I dont think the car is actually "hot", its just an air pocket. I can turn on the heater and it blows cold, when the gage goes back down i get hot air. Seems like it a head gasket I guess, leaking compression it the coolant. Guess its time to take it back down again havent "really" got to enjoy my new set up yet either, this sucks. Thanks for all the replies, later, Chris.............
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