Cadillac Deville over heating problem

[williz57]

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

[niimcoinc]

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.

[maxwedge]

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.

[Yogi666]

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.

[maxwedge]

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

[Demoman442]

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]

Hot96deville same overheating problems

[rotax30]

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/

[maxwedge]

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

[williz57]

Originally Posted by rotax30

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.

[williz57]

Originally Posted by niimcoinc

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.

[IMG][/IMG] [IMG][/IMG]
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.

[2kdeville]

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.

[infree1943]

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..

[erinjbjs1]

It is a great kit and I highly recommend