Cadillac Deville over heating problem

This car started over heating two weeks after i bought it. I brought it in to Lentz auto and they told me it was the water pump...tuffys auto center was cheapest to replace. I got it done (only because u need a special tool to do it and no one around here will let u rent it)*$100* to buy. After they did it the thing ran as good as new. Week later over heated again. Filled it with fluid cause it was low and got it home...took it back. They said there was air in the system and now its running fine. Tryed to drive it 120miles made it about 30 and overheated again. Put fluid in it let it run with cap off and got all the air out and it got me back home. Brought it back AGAIN and they told me the only thing it could be is the head gasket. They SAID they chemical tested it and it was bad. I have been letting it sit for a whle now and decided to look at it with my dad. Ran it...filled the fluids after we took the thermostat out(by cutting everything off but the alluminum top with seal)turned it off after temp was raising. Let it cool down a bit checked level...was full. Took off top hose going from radiator to motor.... It was cold by the way and now pressure... blew threw it into the radiator and fluid came out from where it meets the engine. So we figured no circulation...So i brought it to tuffys and told them its gotta be the waterpump again. They checked it...drove it said it runs rough and its been over heated to many times and its the head gasket. He also said that there was a coolant leak and he fixed it. It was one of the heater hoses comming from the engine into the firewall. So now the top hose has pressure and is getting hot. The top and bottom of the radiator is getting hot...never used to. The heat works again. But when ur driving it thew town the temp stays arround 190 and 210 for a while untill you drive a little faster and cost down hill. Then it starts to go to 233 ..thats when i figured out.. if u park the car and tap the gas to get the rpm's higher the engine temp will go down...drastically. 233 to 197:screwy:
Some one has to know what the deal is??
I will reply with the electrical problems later but this is my biggest consern. Although i can drive it at least now.

but for the head gasket
-No milky oil
-No fluids comming from exhaust
-Runs great
it does have a misfire but it had before..i replaced the spark plug and it was fine...now the comp says cylinder 2 it was on the other side last time. If it is the head gasket...how common is it for both sides to go out?

HELP!:banghead:

Put a new 195 deg OEM or Stant stat back in. Don't buy a cheapie. Top off the coolant. Pressure test for leaks and repair as needed. Drive it normally for a few days, checking the coolant level each day. If you don't lose any coolant, it is unlikely a head gasket has blown.
Are the cooling fans coming on around 225 deg?

Yes the fans are comming on. There isnt a thermostat in it right now, do i really need one if the heat is still comming on regardless? I drove it today and it seems to be running fine but i have yet to attempt to drive it on the highway cause im afraid i will get stranded.

But i will check for coolant leaks today cause it was full last time i looked at it.

What Year and engine do you have. A quick peek at your Public Profile shows you own a 1998 DeVille so I'll assume thats it.
If they ran the chemical test (we call it a block test) and it failed then you have a head gasket failure(more likely) or a cracked block(less likely). I work in a Cadillac dealer and I can tell you that from your description of your problems it sure sounds like a head gasket failure. Its not uncommon for the threads in the aluminum block to pull out which loosens the tension on the headgasket and causes the failure. There is a special tool kit out in the Cadillac dealerships to repair the threads in the block. They are called Time-Serts and they are simular to Helicoils but 10 times stronger/better. Head gasket repair on a Northstar V8 is expensive (like $2000 - $3000). It requires engine removal to do. Another option is to just have a used engine installed.

I might be wrong but dont they have to take the engine somewhat apart to run a block test?
Yesterday i took it out and drove it and tryed something new...when i drive it in second gear(automatic) and run it at about 35-40 mph the temp went down from 242 to 188-190? Does anyone elts have any other ideas OTHER THEN HEADGASKET? this car runs fine exhaust smells normal....you can smell coolant though i noticed when u turn it off after driving it for a while. Heat still cutting out when temp goes up. *no thermostat in this car*

Check that the waterpump belt isn't slipping. If the temp goes down when the RPMs go up, it could be a slipping belt not giving enough flow. Check that the tensioner is working ok.

...you can smell coolant though i noticed when u turn it off after driving it for a while.


Where are you smelling the coolant? Inside? Front of car? Behind car?

The block test I'm talking about can be purchased at NAPA for $50. Here's how it works. You put this blue liquid in the plastic tube, place the tube cone end in the radiator neck or on your Cadillac, the reservoir, and use the squeeze bulb to draw in air up into the blue liquid while the engine runs. If combustionn gas is present the the liquid turns yellowish. Sometimes they'll turn yellow right away, sometimes you need to load the engine a little or rev it up to push a little combustion gas into the cooling system.http://partimages2.genpt.com/partimages/223665.jpg

I've used that block tester before. I didn't know what you were talking about at first either. It is very easy to use! I'd also recommend the hydrocarbon test before thinking of spending the money on a headgasket replacement.
On my Deville, it turned out to not be the headgasket that was leaking, so that saved me time and money!

I've had plenty of Northstars run normal, no smoke but have a headgasket failure. They don't all just blow out huge. Other possible problems could be a plugged up radiator.

I Have A 99 Deville With Same Problem. I Changed The Water Pump Twice, W/p Belt. The Tool Was Under $20 At Auto Zone.... Changed Thumistate Twice ,ran It Without One For A While, New Hoeses. No Help!! My Car Runs Hot When I Drive Up A Incline... This Was Last Summer. I Stopped Driving It For A Few Months. While Trying To Find Problem... This Past Winter I Started To Driver It Again And Had No Overheating Problems Car Run Grate For The Last 4 Months...... How That To Weather Is Getting Warmer..when It Hits 70 Deg. Out Side My Car Run Hot Again ????? If It Is A Head Gasket Why Does It Run Good In Cold Weather ??? If I Find My Problem I WILL Let You Know....or If Anyone Has Any Advice Plaese Responed.. Good Luck...

the belt thing sounds promissing. the radiator cant be pluged if i can blow threw it....i will check belt. I also noticed the two hoses going from the passanger side seem odd cause one is hot and the other is not. Are these going to the heater core?

the belt thing sounds promissing. the radiator cant be pluged if i can blow threw it....i will check belt. I also noticed the two hoses going from the passanger side seem odd cause one is hot and the other is not. Are these going to the heater core?

That doesn't really mean anything, you could have a few rows plugged which will reduce the radiator's cooling abilty and still blow through it. The two hoses do go to the heater core. Does your heater work? Because it sounds like your heater core might be plugged. You can back flush the heater core to fix that problem.

heat does work although there is no thermostat in this car and when the temp climbs higher the heat cuts out. But when u get it at a higher rpm...put in neutral and hold has petal down slightly...the heat kicks back on?

I'm having a similar problem my heatercoil went out an my car started overheatin asap so I by-passed the heatercoil an it still overheated so I changed the thermostat I changed the waterpump an its still gettin hot. the oil is still the same an runs good I don't think its the heads cuz as soon as the heatercoil went out the car got hot I jus don't think the heads would go outthat fast sum body help!!

Buying a used Northstar is the main cause of headgasket failure.

My main problem is I lose coolant on my 98 Deville, but have never observed any on the ground. Car runs about 197 degrees, normally, but if idling I've seen 221. Never ever heard the radiator fans come on. Fuses ok, but don't know where to look for relays. Is this normal? I got the car less than a year ago, have put about 4000 miles on it, during which time I have added about 3 gallons of coolant. It always tells me when coolant level is low. I always smell coolant when exiting the car if I walk around near the front of the car after driving it enough to get it warmed up fully.

Second, when I check the coolant level, even after the car has sat overnight, there is still some minor pressure in the system. If it had a leak wouldn’t it lose all pressure? Every time I start the car, it runs rough as if missing on one cylinder, for no more than 30-60 seconds.

About every 50th time I start the car there is white smoke coming from the exhaust for maybe 1-2 blocks then disappears. Not sure I want to change anything since I get 33mpg on the highway.

Is this car reliable for a cross-country trip? If this is a head gasket, could the white smoke be in the exhaust because the exhaust valve at the cylinder where the head gasket is defective happens to be open overnight? Can a minor gasket leak seal itself as the engine heats up? Is there any additive I can put in the coolant to seal the gasket if it is a leak?


Thanks in advance for any response.

Almost defintely a head gasket issue, these engines are noted for this. And no it would not be reliable. There are tests that can be done by a shop to determine if a hd gasket is bad.

Having overheating problems in '98 Deville too. Someone told me that I could have air pockets in the cooling system and that I needed to purge the system to remove them. I think it's head gasket. No white smoke, yet. Flushed cooling system, changed thermostat, water pump, everything but head gasket. Has anyone ever used the pour in head gasket sealer products in a NorthStar engine? As long as you don't gas it to pass someone on the highway, or drive more than a hundred miles and just take it nice and slow with acceleration it seems to be fine. I just want to sell the car but can't with this overheating problem. It is part of an estate liquidation.:crying:

If you have a bad hd gasket no pour in sealer has been known to correct this.

I feel your pain, I have a 2000, I have replaced radiator,thermostat {gm} water pump, cap, flushed everything. runs fine,fans work normally, temp goes up around 220-230f in traffic or with air on then goes normal for a while. block test was normal. Whoever figures this one out will be a hero!

Hot96deville same overheating problems

my dad and i have saw 220-227 degrees out of his 99 deville.changed thermo,water pump,new rad,flushed.has 190-195 lbs. compression.one low cylinder in back,180lbs..still runs warm.whats up with that/

The fans come on at 222, is this all the time, in traffic, hot day, on the h'way? no meaningful info here?

my dad and i have saw 220-227 degrees out of his 99 deville.changed thermo,water pump,new rad,flushed.has 190-195 lbs. compression.one low cylinder in back,180lbs..still runs warm.whats up with that/ A low psi cylinder is bad but not necessarily a cooling problem. temps at 227F are not that far out of the norm and could be considered normal.

Having the coolant reservoir tested for exhaust gas is the step to take if the HG is suspect.

My main problem is I lose coolant on my 98 Deville, but have never observed any on the ground. Car runs about 197 degrees, normally, but if idling I've seen 221. Never ever heard the radiator fans

About every 50th time I start the car there is white smoke coming from the exhaust for maybe 1-2 blocks then disappears. Not sure I want to change anything since I get 33mpg on the highway.



Thanks in advance for any response.
White smoke could be normal cold start condensation blowing out of the mufflers, especially if it disappears after 2 blocks.

I just had to repair a leak on my northstar at the coolant crossover manifold and it was not an easy fix to replace those gaskets.

http://i826.photobucket.com/albums/zz183/billytheshoe/100_1168.jpg http://i826.photobucket.com/albums/zz183/billytheshoe/100_1166.jpg
The blown out gasket is obvious. The water pump/thermostat housing cover is a common leak and its design has been revised.

I was very happy with that outcome not having the doom of a head gasket/bolt failure. It would send my car to the junkyard.
If you put the air conditioning on max cold both fans should be turning, if not thats a elec. problem/bad fan motor.

Heads can leak in so many varying factors, the aluminum itself can degrade enough to allow coolant passage above and or below the gasket itself, pinholes, fine hairline cracks, some expand when warm and make the car hot wen otherwise it will idle for hours without over heating. But when all else fails and you have replaced the water pump, radiator, therm, checked all hoses and your fans are working fine one should then start the car and rev it to 2000 rpm for 5-10 minutes then immediately getting out to view your cad converter which may very well be the whole reason your car is overheating. Its happened to me twice over the years, everything was replaced and all else was functioning beautifully and a car still just overheated, sometimes in traffic, sometimes rollin down the road or at idle. If indeed your cad is clogged up most cadillacs are manufactured with the converter 4-6 inches from the head causing the engine to overheat due to location transfer of heat as well as extreme exhaust gas temps, thereby causing the car to overflow excessively resulting in "low coolant" and a constant unavoidable overheating. Air in the system is a biggy as well, ive worked on cars that were overheating simply due to a large pocket of air caught in the hose that runs along the top parallel to the radiator. Once i loosened the hose, held it up and filled it to the top, clamping the hose so it does not spill while reconneting, these cars were simply missing about 3-4 quarts of fluid, usually also almost always accompanied by little to no heat as well as heat increase with rpm.

I have had some over heating problems with 2004 Deville, and will offer any help I can. First time it over heated was due to a bad radiator cap. Good place to start.
Later had another problem, and found a pluged purge tube. Tube runs across top of engine and is hooked to top of fill reservoir. It is a small line and can plug easily. Then of coarse a defective thermostat, but you have been there.
Check the simple things first..

It is a great kit and I highly recommendhttp://webb.erebook.com/4.jpg