A year ago I bought a 98 Deville, 91k miles,fully loaded and clean at $1800.About a month ago it started overheating 220-240 degrees and display CHECK ENGINE COOLANT LEVEL and CHANGE OIL.I let it cool down and put about 1gal. of coolant.I did notice a leak at the water pump and replaced the water pump along with the thermostat, did a system flush and used DEXCOOL .No more leaks but I am still loosing coolant somewhere at a rate of 150 miles/1gal. of coolant.When I first start the engine there is some white smoke and rough idle for about 30sec. to 1min. and then gone.The car runs great,plenty of power,temperature stays in the range of 190-217 degrees but I'M LOOSING COOLANT.I do suspect it is the head gasket/s but I'd like to keep the car if I can get away with $1000 to fix it.It is clean inside/out,power everything,moonroof,heated seats/lumbar,12 cd changer,2 drivers memory,chrome wheels,garage opener,the whole nine yards.How much would it cost to replace the head gaskets,is it doable in my own garage with the engine on the car (I am a decent home mechanic) and WHY DOESN'T GM DO ANYTHING ABOUT THE OVERHEATING/HEAD GASKET PROBLEM on the Northstar????????? I mean ,for crying out loud,most of the owners have this problem under 100k miles.

Not to sound like a dick, but what did you expect from a 98 Deville that you got for 1800, thats rediculously low of a price, whoever sold you it knew the headgasket was bad. It definetly sounds like you've got a blown headgasket. The quickest and easiest wway to be sure is to get some coolant test strips that will test for exhaust gases in the coolant. You could also go to a radiator shop and have them do a cylinder leak test. The change oil messege came up because the engine fryed the oil when it overheated. The white smoke on start up is coolant in the exhaust, if you wipe your finger on the inside of the tailpipe, there will probably by coolant in there.

As for fixing it, prepare to spend 3000-4000 dollars. That's if you haven't warped or cracked a head or the block from it overheating. Its a pretty involved repair. The motor must be dropped out the bottom of the car, its nearly impossible to get to the headbolts (all 20) with the engine in the car. Then all 20 headbolts must be timeserted (rethreaded into the block). Most of the time its better just to replace the motor.

Did you add the supplement to the coolant?

<br><br>Post edited by: Handsome_Guy, at: 2007/07/25 14:58

I did not.When I bought the water pump from the Cadillac dealer I asked and I was told that their technicians DO NOT USE the coolant sealer and IT IS A WASTE OF MONEY.The parts guy is somebody I know and trust.

The parts guy at the caddy dealer near me told me the same thing about the tabs. Apparently they clog the cooling system, I've seen it happen in my blazer before with a different stop leak/supplement. My mechanic who is very trust worthy told me to put the tabs in, after head rebuilt my engine when the headgasket blew. I am not sure how much they would have helped you though.