Question about 1999 Cadillac Seville STS

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1999 Cadillac STS OverHeating !!!

I have a 1999 Cadillac Seville STS and it is overheating!! has no signs of head gasket failure except overheating. previously it was overheating when i go fast or down hill now after a cooling system flush and thermostat replacement it drives beautifully on the highway and down hill at high speed. But now it just overheats like nothing in the city driving cant even make it home form the shop aprox 10 kms away it just goes straight to the red and overheats. before there was a high pressure build up in the surge tank and the coolant would boil out the fill of the surge tank. now it doesnt boil out the car just overheats completely. this morning the car had 85% oil life on it as it has had oil changed on it but then it over heated today and instantly after shutting the car off to cool down when i restarted it the oil completely burnt out 0% oil life engine light came on, the car had absolutely no oil in it, and now i need to change the oil. could it be air in the system. I bought a bottle of Blue devil head gasket sealant after doing some intensive research and i havent used it because i dont want to use it and the car has a problem it wont solve. NEED HELP ASAP CAR IS ABSOLUTELY MINT WITH 181000kms on it AND IT WOULD BE SUCH A SHAME TO HAVE TO SCRAP IT!!!!!!!

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  • Jamal Mohamed
    Jamal Mohamed May 06, 2014




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  • 68 Answers

A blown head gasket or intake gasket does not always put coolant into the oil or produce smoke.. If the gasket blew between an oil vein and coolant vein then there is a possibility that your actually pushing the oil into the coolant side.. When the car is cool... look at your antifreeze and see if it has the oil slick look to it.. That being said it could be a head gasket or it could be in the intake as well..

Posted on May 06, 2014


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Posted on Jan 02, 2017

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SOURCE: Cadillac seville sts 99 overheating

dose it have an electric fan ? if it does look to see if the fan is working hope this helps.

Posted on Dec 25, 2008

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SOURCE: 1999 cadillac deville overheating

my husband did everything that everyone else did that had this overheating problem. It was so weird that my engine cooled at a light and heated up going down the road. I have a north star 4.6 engine and this is natorious for happening. my check engine light also came on and so I had a diagnostics done which told me my #1 injector wasn't firing , car ran like **** as well. After putting in a new water pump and plugs,ect. and realized injector was good a friend told him we could have a blown head gasket. So just to see if this was the problem I went to buy a bottle of glassbeads and the auto parts guy told us to purchase a bottle of BARS STOP LEAK BLOCK SEALER NOT RADIATOR BUT BLOCK SEALER $31.99 . He followed the directions and we waited 24 hrs. before driving it. What ever the problem was has stopped my car runs like brand new and I am loving it again. no over heating no injector problem, runs great.......I hope this helps. I know its probly a temperary fix but its a fix and now we know what the problem was. SASSY

Posted on Mar 19, 2009

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SOURCE: 99 Cadillac Deville Coolant Leak

Most likely a cracked block or free plug that came out or loose. Other options are hozes, which I believe the dealer would have fixed. A third option is the water pump itself. 

Posted on May 06, 2009

  • 135 Answers

SOURCE: 2000 cadillac seville sts- it is overheating only

check to see if cooling fans are working. if not replace fans or fan sensor. check oil. if there is coolant in the oil, you may have a cracked head or a defective head gasket.

Posted on May 15, 2009

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SOURCE: 1999 Cadillac Seville STS Overheating

Sounds more like an ignition control or coolant flow problem. Or, a/c fan not coming on with a/c.
Getting the water pump question out of the way, the pump either works or not. If it leaks it will cause an overheat due to coolant loss on flat ground or grades...doesn't matter. If the pump bearing or seal is bad it will still pump, it will just be loose and noisy. Coolant flow through the radiator is also essential...I don't think you have a problem there because generally this happens with less maintained higher mile cars.
A bad map sensor can cause your problem because it changes both ignition timing and fuel mixture, either of which can cause very high temps in combustion chambers especially when under a load. Mass air flow sensor can also do this but usually will cause idle problems. If fan is not on with a/c if the remainder of your cooling system may be enough to maintain decent temp control but cannot do this under a load. A/C turned off removes some load and therefore allow you to get up hills. Operating marginally, you can be pushing some coolant out of the system at times without even knowing it.
Now, about your engine: These engines are in my opinion a very poor design to begin with. Even with the best maintenance and low miles, they don't handle temperatures well. at this point, I'd be concerned that after repeated overheats and near overheats, your head gaskets may have started to fail, even though they were not the cause of the problem.Keep that in mind.
Have the items I mentioned tested. If you finally have the problem solved I suggest you change the thermostat as well...Overheating makes them unreliable.

Posted on Jul 27, 2009

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