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2002 Cadillac Deville
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2 Posts
Discussion Starter #1
I'm new to the Forum but I could really use some Expert advice! My wife purchased an 02 Deville from Auction, Drive home from Auction about 40 miles absolutely fine. The Daughter took it that very evening for a Babysitting job and as soon as she got on the Expressway the Car Overheated! Read up on the Northstar engine and discovered the Head gasket issue. Did a Block test on the Engine and it consistently showed a negative result, even when the car was overheating! Verified the Fluid did change colors by checking the Block tester on the Exhaust fumes, changed colors. Tried the Block test on the Engine, again, still negative. Replaced with New Parts the Following: Radiator, Thermostat, Temp switch in Block, New Upper and Lower Radiator Hoses. Verified Fans kick on and Purge line is clear. Car continued to Overheat! Decided, although negative Block Test, that the Head Gasket must be blown and purchased Stud kit for replacing the Head Gaskets. Was able to replace the Front Head gasket but unable to access the rear will attempt to drop engine in the spring to get to the rear gasket. Put the Car back on the Road and it was able to hold engine temp within one or two levels from normal for about 2 weeks. Daughter and Boyfriend, got the car stuck in the snow and overheated the engine, Now The car continues to Overheat after running for approximately 30 to 45 minutes. Any thoughts or ideas would be appreciated!!
 

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2001 Deville DTS
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136 Posts
Much more experienced guys will chime in, and they may even move this to the Northstar section.

My initial thoughts: The block test isn't fail safe. Do you have pressure buildup (when cold) in the reservoir? Are you using coolant? My worst cylinder was #1, which is in the back.
 

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2002 Cadillac Deville
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2 Posts
Discussion Starter #3
No pressure build up when cold. Pressure builds once it's warmed up. Yes on use of the coolant. Thanks for your thoughts!
 

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2001 Deville DTS
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136 Posts
I should clarify: Yes, it will build up pressure when warm, but when it is COLD and you open the reservoir, does it have pressure? (It shouldn't unless exhaust gasses are getting in)
Use of coolant could point to headbolt issues, but still doesn't mean it's not going somewhere else.

It would be cut and dried if you were getting a positive block test. Without that, I would verify ALL cooling issues before dropping the engine. Hopefully others will chime in to help you troubleshoot / verify all aspects of the cooling system.

Being it was at auction, it could have had some stop leak added, or mixed DEX COOL and green, or who knows what else. You could have something clogged. Have you 100% verified with pressure tests, etc? Does heater work fine?
 

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1998 Seville STS, 2003 Deville
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282 Posts
Have you tried the block test again since it was overheated in the snow bank? The test needs to be done with the engine at operating temperature. just be careful when removing the cap on the expansion tank. I believe it's the rear head gasket that typically goes bad first and you have not changed it yet.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,478 Posts
The Engines; Northstar forum. Please read the sticky posts on the main threads page.

You are throwing parts at the car, hoping one will stick. This problem sounds like another coolant purge line problem.

Google "cadillac forums northstar coolant purge line cleaning".

The cooling system is supposed to build up considerable pressure when hot - that's what allows it to safely run at 210 degrees 24/7/365.
 

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2003 DTS
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205 Posts
Ummmm did you happen to try replacing the reservoir cap? Or doing a pressure test to see if you're maintaining pressure in the system? Without pressure, the cooling system just doesn't work at high temp.
 

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1998 Deville
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710 Posts
I hate to say it and it means nothing now you are stuck, but these are not the cars to buy used. Especially with anything over 100k miles. They are money pits. My advice, fix it best you can and sell it for whatever you can get. It will nickle and dime you to death if not worse. It isn't just the head gasket. Everything else is going to fail too. Coils, o2 sensors, cats, power seats, heated seats, electric window motors, fans, A/C, etc, etc. Keep a spreadsheet with how much you are spending. It will help you to get rid of it. Even though you are "pot committed" right now really you are not. This car can cost you SO MUCH more. It is never ending with shit that will break.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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26,323 Posts
Post #1 states that the car overheated on the freeway. The cooling fans serve no purpose over 25 or so MPH.
 

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White Diamond '03 DHS (with DTS floor shift)
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86,785 Posts
This is most likely the reason it was put through the auction.

How many miles on this car?

Are you having to add coolant regularly?
 
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