Help! 99 Cadillac Seville STS overheating - just after buying it

About 5 minutes driving my “new” STS home from the used car dealer, it started to overheat. It was already at operating temp when I picked it up, they had it out for a wash and to put some gas in it just before I took it.

About 5 minutes into driving home, the temp gauge started to move up a little towards the red, then back to the middle…then back up…then back down, then back up and then kept climbing. This was in some stop and go traffic, but nothing bad. Then it kept going towards the red and as it got close to the red, I pulled over and called the dealer back…he had me check the fans (both were running) and the upper rad hose (it was hot). I then turned of the engine (but the temp was starting to go back down on the gauge at that point). The dealer said to leave it for 10 minutes, then bring it back, turning the heat on full to dissipate some of the heat.

Well, I waited 20 min then started it (temp was at half mark), and after about a quarter mile of driving, the temp just kept climbing back to the red, so I pulled over into a parking lot and turned off the engine.

No coolant was seen on the ground either time, or any plumes of white steam seen from the exhaust by my wife who was driving behind me. BUT this car does have the 4.6L V8 Northstar engine, so I’m thinking head gaskets…?

The dealer got the keys from me and said he’d check it out, do a pressure test, and they have not tried to pull any “sorry about your luck, you’re on your own now, papers are signed” BS. I have a 1 yr warranty, but through a 3rd party company. When I test drove the car, it did not overheat (maybe I didn’t drive it long enough), and the dealer is surprised, said it did not overheat with them.

Questions…is this something they probably knew about? If so, how were they and I able to drive it before? Does it sound like a head gasket or something else? What should I be asking/demanding tomorrow when I call to get their diagnosis?

Any and all help is appreciated!!

Can anyone give some advice? I’d like to hear some feedback before talking to the dealer tomorrow.

Does anybody check anything anymore? If you had looked in Consumer Reports, you wouldn’t have gone anywhere near that car. It’s rated as close to scrap metal as it can get. I wouldn’t have it if it came with a 20 year warranty. The cooling system was one of the three thinga that were rated above average for reliability. Seems like you are down to just two now. Two out of three ain’t bad unless you have nine other categories that are rated as lousy. You can’t blame any malfunction on the dealer. They know that anybody buying one of these is nuts. It could be a bad sensor and you might have a lucky month with the thing. See if they will take it back and only keep a thousand dollars. Get the subscription to CR and give yourself a chance next time. You’re experiencing the Army equivalent of getting awarded five purple hearts on your first mission. Your Stargate address just dropped you into a black hole.

That wasn’t helpful.

You should be asking to get it repaired, and if they don’t want to fix it, they should be giving your money back.

In your locale(state) it really depends on any warranty period and what you signed. You could get your money back.

If you have a third party warranty, they pay (hopefully) so then get it fixed that way.

If ownership is short lived, one major huge piece of advice. ALWAYS have a used vehicle checked over by mechanic before purchase. Especially a car past the 7yr or 150,000 mile check no matter how wonderful it drives. Lastly if your buying used take the car out for half the day if considering purchase. If they won’t let you tell them your not interested in doing business with their establishment.

Questions…is this something they probably knew about? If so, how were they and I able to drive it before?

Probably not. More than likely, they never drove it any appreciable distance and if they did, the people who drove it weren’t paying attention. The dealer’s response is another clue. They’re not trying to dodge responsibility at this point and are being helpful.

Does it sound like a head gasket or something else?

It could be many things. Best to wait for their diagnosis.

What should I be asking/demanding tomorrow when I call to get their diagnosis?

They should fix it for free and in a timely fashion. If it will take more than a day or two, I would suggest they provide a rental/loaner until it is delivered fixed. I would decide how to handle it as the situation unfolds and how they treat you during the process.

Thanks everyone, good advice. I will talk to them soon and let you know how it unfolds.

Well, I talked to them this evening, the owner said he did a coolant flush and changed the thermostat, and they’ve been driving it around today and it’s never gone past the half way mark (where it’s supposed to be). He said there could have been air in the lines…does that sound plausible?
He said he’d drive it home tonight and then back to work to make sure everything is ok. Says they did do the pressure test but the gaskets were fine.
So, unless something changes, he’s bringing the car to me tomorrow night.

Any comments from anyone based on the above info?
Thanks again.

It’s possible that an air bubble moved and either went in to the water pump or blocked a line or passage completely, yes. If he drives it around and it doesn’t overheat, then you’re good. But wouldn’t it be nice to get it in writing that if it happens again in 100 miles / 1 week that you can take the car back?

Yeah I agree, but he says that the warranty company will cover any problems, and that if his shop was to do any work on it from here on, it would be through the warranty company anyway. So, we’ll see. He has to drive about 60 miles to bring the car to me anyway. Thanks for your reply.

It was helpful to anybody reading it who is considering buying that make, year and model. That post could save you and others thousands of dollars throughot his/her life. If a person is buying cars with absolutely no information, some kind of guide will definitely help. A $4000 car can cost $1500 just to make it safe to drive. Now the $4000 cars cost $9000. Prices have gone up since the late nineties. With the price of everything these days, people owe it to themselves and their family to do at least a little easy research before figuratively getting their wallet and savings amputated. I hope the message gets through. Nothing beats success. Some failures are avoidable. Be at least a little careful.

Another update…the dealer called me on his way with the car and said he wasn’t too happy with it, he was in stop and go rush hour traffic and it was starting to heat up again, not to the red zone, but about 3/4 of the way…when he was at highway speeds, it was fine. So he didn’t want to bring it to me like that, and thinks it may be the water pump now. Says the rad looks new-ish, so it’s probably not clogged, and insists that the leak down test showed the head gaskets to be fine.
So, tomorrow I will get (hopefully) the correct diagnosis. What do you guys think it could be at this point? Seems strange to me…could it still be a bad thermostat? What else can cause overheating like this? He says it’s not losing coolant.

If I were seeing the problem now. I would think that a fan switch wasn’t working or the temp sensor was getting funky. The fan switch or fan motor is the one I favor at this point. He can probably make the fan stay on by disconnecting the fan switch. Some systems work that way. The fan could be hot wired for that. I think you are getting somewhere with this problem.

Well, when it overheated with me, both fans were running. I did think about the temp sensor/sender…could it all be ok and just getting the wrong temp from the sensor?

Well, they finally diagnosed it - head gaskets! They are replacing the heads, gaskets, and putting Timeserts and new head bolts in, all on their dime. Which is awesome. Is there anything I should replace or monitor (other than temp) after this is all done and I get the car?

Get it to an independent mechanic or a dealer for a thorough check!