Question about 1998 Cadillac Seville

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Losing coolant 1998 sts northstar after about 30 minuets running it around the temp gauge moves up to H and i am losing coolant , there is no white smoke , and the exaust does noy smell sweet . pleease help

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  • eric forbes
    eric forbes May 27, 2008




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It's usually the water pump...driver side just under the cam driven belt. If you let your car get too hot you will ruin it's aluminum engine.

Posted on Oct 01, 2008

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Please check the radiator it may be leaking or there may be hole in the coolant container or the sensor is defective get it checked ..................................

Posted on May 27, 2008


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1999 Cadillac STS Overheating

i would have to say ck. the easast things first,when was the last cooling system flush making sure all cooling system parts are clean and new coolant added(old coolant looses its abilaty to work properly when old)then have the thermostat ck to make sure it opens and closes at the proper temp.

Mar 25, 2014 | 1999 Cadillac Seville STS

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01 sts head and gasket good replaced water pump thermo rad cap works good for 2hrs then over heats and no heat im stumpted cooling fans maybe i cant figure it out a bad thermostat even though it was just...

The temp gauge being erratic should have been your sign. Are you sure its overheating or are you going by what you see being registered on the temp guage.Also after doing work such as water pump sometimes you will get air lock in the system you need to bleed the system after performing such a job. If the temp gauge is bad you need to replace it.

Jan 02, 2010 | 2001 Cadillac Sts

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I have a Cadillac 2000 STS with the V8 Northstar engine. Can you help me locate the water temperature/coolant sensor. I am trying to get thru why it is boiling over the resevoir box and into the engine...

This could be a faulty surge tank cap, common problem.
The cap is designed to hold 16 psi pressure,if it fails, the coolant will escape.
The cap only costs a few dollars so it's worth changing it to see if this solves your problem.

The Engine Coolant Temperature (ECT) Sensor is located on the Left hand rear corner of the engine, below the exhaust gas recirculation valve.

Also, the fans don't come on until the temp reaches around 225 degrees.

Oct 21, 2009 | Cadillac STS Cars & Trucks

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The cooling fans wont kick in and its boiling

The most common overheating problem with the Northstar engine is a blocked purge line. It's job is to purge air out of the cooling system.
If the purge line is blocked you may have an air lock preventing coolant flow.
There is a small diameter hose coming from near the top of the coolant tank,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.

Air locks in the Northstar engine shouldn't be a problem as the system is self purging, providing all the hoses are clear.

Check the coolant level in the tank,it should be half way when cold.
There is no cap on the radiator as it is a fully pressurized system.

The expansion tank is the only means by which to add coolant to the Northstar engine.

Check to see if your fans are working by switching on the air con,they should run all the time.

With the air con off,the fans won't come on until the temp hits around 225 degrees.

Also, if it's boiling over, the cap on the expansion tank may not be holding pressure and therefore needs replacing.....a new cap only costs a few dollars so it is worth replacing to see if this solves your problem.

Oct 09, 2009 | 1998 Cadillac Seville

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Whats normal operating temp for 94 sts northstar

The thermostat opens at 196F, but sitting idling, the coolant fans may not turn on til' 125F.

Sep 22, 2009 | 1997 Cadillac DeVille

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My STS ( 180000 miles) is overheating in traffic

Dude KravCar i seriously want to thank you for helping me fix my car!!@! i have a 1995 Oldsmobile Aurora Northstar 4.0 V8 and i came across your response to someone who was having an overheating problem with their Northstar commented for them to remove and inspect one of the purge lines to bleed out the air........ now after countless hours in my garage and wrongful diagnosis from a repair shop i finnaly have my engine running back fine after reading your response......thanx dude

Aug 06, 2009 | 1998 Cadillac Seville

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98 Deville Northstar temp runs up to 240 when idle

Yes it is headgasket. Mine had same problem. Yours might not be severe as of now, you can try these other solutions. THERMAGASKET... Which you can buy online, and get your money back if it does not work... And stuff in a bottle at Autozone Repair headgasket with NanoTechnology! I would try and sell it quick, because these engines are very costly to repair and most mechanics wont even attempt headgasket repair, and plus you have to TimeSert the block...

Nov 24, 2008 | 1998 Cadillac DeVille

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Overheating bigtime

did you check the oil?does it look milky?

May 27, 2008 | 1998 Cadillac Seville

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Overheating bigtime

Is the temp gauge high?Does the car blow white smoke?Check the oil and see if you have antifreeze/water in the oil.You may have a blown head gasket.Im assuming you have a norhtstar motor.

May 27, 2008 | 1998 Cadillac Seville

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