: Overheating problem just started.

07-30-06, 01:03 AM
Yesterday while driving my 1999 Deville D'elegance it displayed a message that it was shutting my air conditioner off because of my engine getting hot. i switched over to display the temp on the dash and it displayed 255 degrees. I immediately pulled over. I had lunch and then got back in the car and drove back to where I work. It had overheated once again on this 5 minute trip. I decided to call the dealer and well they said that it probably blew a head gasket. I am sorry I refuse to believe this. The car has 97,000 miles on it but it is cherry..........it even still smells new on the inside. I went ahead and replace the thermostat in it. I replaced the coolant and started it back up and finished topping it off with coolant. I ran it for about 30 minutes and it seemed to do fine. So I took off for home and in about 15 minutes of driving the car it overheated again. So I had it towed back to my work. A mechanic today looked at it and is baffled as to why it would be overheating. It ran hot once while he was looking at it. It happened when he started revving the engine up. He shut it off and restarted it and then while idling it cooled itself back down. I asked him if a waterpump could be weak while the car is being driven he said no. I asked him if my headgasket was blown. He put his finger in my tailpipe and said no. Later in the evening after the sun went down I refilled the coolant that was lost from when I had it towed and it made it all the way home without going over 206 degrees. Not real sure that is fixed. Anyway I noticed some talk about a purge line might be clogged..........where is this?
I really hope that maybe someone can give me some kind of idea of what is making the car overheat and how to make sure it won't happen again. I drove it tonight 20 minutes home and left it run for about 20 more minutes in the drive and it didn't overheat but I am scared it is not fixed because nothing else was touched after the thermostat was put in.

Thank-you in advance for your help

07-30-06, 08:22 AM
With some reading of other posts in this forum you will find exactly every answer to your questions. I've diagnosed and repaired my car several times by doing exactly that, including the headgaskets and time-sert repair. You or your mechanic need to do a compression test and check for exhaust gases in the coolant. The Nstar rarely mixes coolant into the oil for a bad headgasket.

Be sure to check your surge tank and small hose that connects it to the water neck. They can get clogged.

Have you been getting a warning for a few months every so often that says your coolant level is low?

07-30-06, 08:26 AM
Here's a link to another similar post with more details on what to check.


07-30-06, 08:39 AM
I saw this thread...........thanks. To answer your question about losing coolant ...no I have never got any warnings. Where is the purge line so I can check? Also how do I check the belt tensioner to the water pump to see if it is slipping? My mechanic is gone until Thursday to ask.


07-30-06, 10:52 AM
Ok i found the purge line and it didn't appear to have much in it to have blocked it up. Next question how do you check the water pump tensioner belt??

07-30-06, 01:58 PM
Pressure test your cooling system! Yesterday I got a "check coolant" message, so I immediately had it pressure tested and sure enough, there was a big leak in my radiator that would have overheated me within a couple days if i kept driving. Point is, when u pressure test it you can start eliminating a bunch of possibilities.

07-30-06, 02:15 PM
On the engine end of the purge line it is attached to a hollow bolt. This is where it would be clogged if it is. To check mine I just took the surge tank end off and blew a short blast of compressed air thru it. You could just use your mouth...you will know immediately if this is clogged. Pressure testing is an excellent idea. My radiator passenger side tank was cracked and leaking requiring replacement just before the headgasket problem showed up and probably was a contributing factor.

07-30-06, 02:17 PM
Ok i found the purge line and it didn't appear to have much in it to have blocked it up. Next question how do you check the water pump tensioner belt??

The water pump belt is driven off the back end (drivers side) of the front intake cam. It has a guard on it held on with a couple of 10mm bolts. Just take the guard off to inspect the belt and tensioner.

07-30-06, 03:14 PM
Ok as far as I can tell all of these things are ok. I also compression tested the vehicle and there was no significant difference in compression. I had my radiator cap pressure tested and it tested ok sometimes and sometimes not. So I bought a new one leveled the fluids off. I let the vehicle idle for about an hour temp never went above 220. It mainly rode around 206. I took it for a 45 min drive and the hottest it ran was 222. So maybe with everyones help I now have a good Deville again!!:)


07-30-06, 04:51 PM
That's great news!

07-30-06, 09:30 PM
A compression test won't tell you anything in regards to a head gasket. To confirm or rule out a head gasket, you need to do a cylinder pressure test by pumping up each cylinder at TDC, compression stroke with shop air to 125-150 psi and look for bubbles in the surge tank.

A failing head gasket in the early stages will usually not over heat at idle, but when pulling a grade or at WOT it will.

I am not saying this to scare you or to incinuate that your head gasket has failed, but to give you the proper information for the correct diagnosis if it happens again.

07-30-06, 10:42 PM
I stand corrected for giving the wrong advice. That is what I was thinking....silly fingers just typed the wrong words. Thanks Ranger....I used lots of information from your posts and others to repair my headgaskets.