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Discussion Starter #1
Thanks all for this great forum. I bought a 93 Seville STS 4.6 last weekend from an auto auction, with 144,000 miles on the odometer. By Monday the car was parked because of an overheating problem with pressure building up pushing coolant (about a 1 1/2 gallons) out of the pressure tank vent hose and water vapor coming out of the exhast. After all the reading I was sure the dreaded head gasket repair was in order. First bought a new pressure tank cap, did'nt help. Checked vent tube and hollow bolt coming from the water pump area, all clear. Pulled hose where thermostat is to go, no thermostat :hmm:. Went to store and bought one (180 degree) put car back together and added fluids. Car now maintains 207-212 degrees. Did a few WOTs and temp went to 215 then back to 207. Everything seems to be working well, and no more water vapor is coming from the exahst. I'll now more as I drive the car over the next couple of days and follow up with a post as to the final verdic.

One thing that was strange when tring to figure this problem out is that it appeared that the non-existant themostat was opening up at about 220 degrees, viewed via the pressure tank and watching for fluid movement. Withing a few minutes the "engine coolant hot" warning would appear and fans going full blast could not cool the engine down.

Again, thanks to all for using this forum to post their problems, experiences, and expertise.

Paul Kohut
 

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1994 Sedan Deville
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:welcome: Congrats on the purchase and the repair.
 

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13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
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I take it your coolant wasn't getting a chance to cool down in the rad, being there was no stat in the system.
 

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White Diamond '03 DHS (with DTS floor shift)
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Eldyfig said:
I take it your coolant wasn't getting a chance to cool down in the rad, being there was no stat in the system.
OK, that sounds logical but, how was coolant getting into the exhaust system and what has stopped it?
 

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13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
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Did he misdiagnose water vapor in the exhaust...hopefully?
 

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White Diamond '03 DHS (with DTS floor shift)
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I dunno, but he said it stopped after installing a stat.
 

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1989 Sedan DeVille is now just a fond memory ....
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And I would add, you mentioned putting a 180 stat in there, is that OEM temp? If not, I'm not sure how adaptable Cadillac's ECM's are, I know that others sometimes have trouble going into 'closed loop' with lower temp t-stats.

Something to keep in mind. Just keep an eye on it and if you still have problems, t-stats are cheap.
 

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White Diamond '03 DHS (with DTS floor shift)
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Kev said:
And I would add, you mentioned putting a 180 stat in there, is that OEM temp?
Not positive but I don't think so. I thought it was 190 or 195.
 

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Discussion Starter #9
I asked for a 195 degree thermostat, but the Autozone computer stated 180 was recommended.

Update: Took car out for drive last night and drove for about 30 miles. This included highway and a very steep 23% grade that is about a mile long. The first 2 times I went up the hill the temperature reached about 245 degrees. The third time up the hill the temp reach 255, then the car overheated. As I drove to a place that I could pull off the road I could see a water line trail (clear in front of me). Let the car cool off and added 1 1/2 gallons of water, and drove home.

So though the car doesn't overheat as fast as before it is still pushing coolant out of the overflow vent and utilmately will overheat.

Will take the car into the shop this week and have the leak down test done.
 
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