Question about 1998 Cadillac DeVille

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My Cadillac overheats if put onto the highway. It was running fine after putting in a quick fix called thermagasket due to the car overheating after just a few block drive. This fix began to fail approx. 3 weeks after installation. It doesn't lokk like it's a head gasket. The car rubs too smooth with no mixture of oil, water or antifreeze. I am wondering if anyone can help me. It has been tested with no code for the coolant system.

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Yippers, what happens is compression comes into the coolingsystem and that blows out the coolant.. Been there, done that, very costly to fix correctly. Issue is with head studs, they pull out of the aluminum block. Needs bare block on bench to fix correctly... Measure for exhaust in cooling system, and you confirm the bad news.

Sorry, I did mine, but waaaay too much money to do it

Posted on Sep 04, 2010

  • steveneddy Dec 13, 2010

    These year model Cadillacs with the NorthStar engine have issues with crack/warped cylinder heads and head bolt threads coming literally out of the engine block.

    This was a poor engine design at best. The best advise would be to sell the vehicle and take your losses. There are better Cadillacs out there - most of the best ones are from 2006 and up.



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If your having to put that much water in it I would lean towards a bad head gasket your other symptoms would make me think possible water pump. I'd check them both 1 of the 2 is most likely the prob or possiobly both. Good luck.

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We need help with an overheating problem on our 1999 Cadillac DeVille. We've replaced many parts and wonder if it may be air in the cooling system. Please help.

Could be.
Has the thermostat been replaced ?
You could run the engine without the radiator cap to see if the system has air pockets.
A restriction in the exhaust could cause the engine to run hotter on the road than on short trips.

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Can running a qt oil low cause spike in temperature cool down. Was 222 now 228 and scaring me. Thinking about trying Thermagasket for head leak.

Running one quart of oil will not cause engine to overheat under normal conditions. If you suspect you have a blown head gasket no product such as Thermagasket will fix this problem. You will need a new head gasket installed. A compression test will verify if you indeed have a blown gasket. If you are loosing coolant with no apparent leak, see white smoke from the exhaust, see a grey foamy substance on the underside of the oil fill cap, you probably have a blown head gasket. You need to have this looked at by a professional or you may destroy your engine.

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1997 cadillac deville engine is overheating. can your ''thermagasket kit'', be used on 4.6L northstar 32 valve V8 engine. If so, approximately how long will the treatment last and how much does it cost?

When you say thermagasket kit,I assume you mean one of those silly DIY gasket sealant liquids that you put in the engine.

You should not use these type of products on ANY engine let alone the Northstar.

To cure a headgasket leak, replace the headgasket.....there is no miracle cure.

On the Northstar, you will damage the cooling system,plus you will continue to have issues as time goes on.

How do you know you have a blown head gasket?

Here is something to consider.......

The most common overheating problem with the Northstar engine is a blocked purge line(small hose).The purge line is designed to purge air out of the cooling system.
There is a small diameter hose coming from near the top of the coolant tank (not the cap) ,this is the purge line.
With the engine idling,pull the purge line from the tank,if there is no coolant flow from this small hose,it is blocked and this will cause overheating.
If the hose is clear, check for blockage at the nipple on the tank.Or trace the hose back until you find the blockage.
The hose goes in to the engine to a crossover and comes out the other side close to the thermostat housing,the blockage may be there.

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