Greetings and thanks for letting me join your group.
I have a 1997 Deville Northstar. Over about the last year or year and a half I have had problems with overheating. The water-pump, hoses, over-flow resevoir, thermostat, radiator (twice), basically the entire cooling system, has been replaced. The radiator has been flushed, and we have used the tablets after replacing every major component.
I have had it to the local dealer, and they immediately recommended $5400 worth of work (then having the nerve to tell me on the phone they dont recommend putting that much into a car that old could they connect me to a sales agent?) replacing head gaskets. With that news, I figured it wouldn't to try one of the sealing products which seemed to help for a bit, but can't honestly say for sure that it did.
The car will run at normal operating temps for awhile before starting to overheat. And running engine faster does forstall quick overheating, but will keep going up once it starts, either way.
I took it to another mechanic who said it's not a head gasket issue. But he couldn't tell me what he thought the issue really was.
The car runs beautifully, as good as it ever has. There is no smoke, no water in the oil. So those things, plus my wishful thinking, make me think the second mechanic was probably right.
It does seem to be losing water even tho I dont see where. So whether that is due to overflow or a leak, I'm not sure. We have used the dye but can't see anything under the blacklight. Not that it matters because when it was leaking out of the water pump on an earlier occasion we couldn't see that leak, either. So it could be leaking and I cant see it. There isn't much room under that hood for exploring.
It has gotten to the over-heated point once, but since then when the temp has started to climb it has been turned off and parked. It has been been to both mechanics since it over-heated.
Well, I tried to answer any questions in advance, so please forgive my longwindedness. Hopefully it'll help.
If anyone can give me any ideas where to go or look at this point I would greatly appreciate it.
Hope you all are having a good one.
Mike

 

The head gasket issues isn't the typical failure you are used to.
The head bolts screw into an aluminum block. If the threads begin to pull out you get combustion gasses entering the cooling system.
No loss of coolant, no mixing of water an oil just unexplained overheating while driving.

Search this site i've posted about it several times.
I would help more but am real busy this week and next.