: Overheating and low oil pressure

07-06-06, 07:33 AM
I have a 1996 Deville...

For about the last month, the car would warm up pretty quickly if I was idling. I tend to sit in my car at lunch, run the air and listen to the radio. When I park, the temp might be around 196, where it would stay for maybe 10 minutes. Then slowly it heats up, eventually getting to around 230 where I would turn it off. The same thing would happen at lights as well. Once the car was warmed up, sitting at a long light would heat the car up to around 230, but then driving would cool it back down to around 200-212.

Yesterday at lunch, my a/c all of a sudden stopped blowing cold. This a/c is nearly new, having replaced it less than a year ago. At the same time, I also received a "check oil level" message. I checked it, but it was fine.

4 hours later, when I left work, the a/c was blowing cold again. I drove about 5 miles to the gym, and worked out for an hour. When I got back in my car, the a/c was still blowing cold, but within 5 minutes the car began to overheat. It would still cool down "a little" when I drove, but not enough to feel safe. Basically it was running in the 240's. So I pulled over, let it cool down, and checked the coolant level. It was fine. Checked oil again and it was fine as well.

Decided to let it cool off and try again, but it quickly heated up again. So I had it towed. When the tow truck dropped me off, and I started it to move it into a parking space, I received a beeping and a message telling me "low oil pressure, turn car off".

And that's where I'm at now. Any help would be greatly appreciated. Thanks!

07-06-06, 11:10 AM
Either you are very unlucky and have several seperate issues (A/C, overheat & low oil pressure) all at the same time, you have an electrical problem that is triggering false warnings. You need to verify actual oil pressure with a guage and actual coolant tempurature. Check the water pump belt tensioner, and purge line to be sure it is flowing. Also pull the DTC's.

07-06-06, 11:20 AM
Well the a/c wasn't a warning, it actually stopped blowing cold, and then started blowing cold again during the last drive. I actually watched the temp readout go up as time went along. Hit 250ish and I got the overheating message, and I immediately turned the car off. Could that have been false? I agree about the oil pressure though, as I've seen in some other threads that overheating can thin the oil out enough to give the "low oil pressure, stop engine" warning. Plus it's probably been 4 or 5k miles since the last oil change.

I'm stressing over the possibility that the head gasket is toast, but I haven't seen any sign of smoke from the tailpipe, or milky oil. Still, it's only been the last month that I've had issues with it running warmer when idling, and seems to have become worse as time went along. Since it wasn't overheating while driving, I wrote it off for the time being and just made sure I didn't idle long enough to cause a problem. It always cooled down to good temps while driving.

07-06-06, 09:43 PM
False indications are always a possibilty. A head gasket can go bad in several ways. If it is breaches such that a cylibder is pumping hot exhaust gasses into the cooling system, you won't see any steam or coolant in the oil, but it will certainly overheat and then the exhuast gasses will vent out the cap as it exceeds 16 psi. Might be time for a cylinder pressure test, or start the engine cold with the cap off and look for bubbles before it heats up. If it is putting exhaust gasses in the cooling system you should see bubbles pretty quickly and may even smell exhaust in the coolant tank.

07-06-06, 11:40 PM
Raise the hood let it idle. Both fans should come on above 195 and cool the engine back down to 195. Fan speed is variable and will increase as temp goes higher. The left fan should rev up to high speed at about 210 and stay there till demand is met,or if more cooling is needed due to air condition running. You say the car only overheats at low speed or idle? If it is ok at high speed then the first place to look would be the fans. When the car overheats the computer turns off the air so that is normal. Also at 250 + the oil really thins out and pressure will drop. I have a 96 Concours but the 96 Deville should be close to the same temps. In any event the fans should be blasting at 220! Let us know what you find.

07-07-06, 09:42 AM
Sounds to me like you either have a fan issue, or a coolant system flow issue. The heating up at idle, and cooling off while driving (air flow through radiator) seems to support this. If it isn't the fan, then I would start with the waterpump. Make sure that the belt isn't slipping. Then change the thermostat. It may not be opening all the way, impeding flow. Then check the radiator. It may be partially plugged. Me, if the radiator was plugged, I would replace it. But you can opt to have it cleaned out. It doesn't seem like a head gasket, as your temp should raise, instead of drop, when you are driving. But anything is possible.


07-07-06, 10:45 AM
Whoa Tonkin, Where are you getting those numbers from? Cooling fans do not turn on low til 224 degrees and go to high at 230. They are on continuous when the A/C is on. Normal operating tempurature is about 206 - 213.

07-07-06, 01:04 PM
Ranger, that is what the temp says on my 1996 Concours when the fans come on at. That is using the temp readout on the car. Maybe the temp readout on the Concours is reading low? You are correct the factory manual give the temps you stated. The air conditioning turns the fans on when the high side refrigerant exceeds 50 C. In any event I love the fact that the car temp is 195/220 F temp even at 90 F with air blowing full in stalled traffic. Says a lot for the engineering of the cooling system. Can't say the same for my Blazer. Thanks for the correct info!

Bill Davis 2i
07-08-06, 06:26 PM
Greetings, I too have experienced What I believe is a False reading of Over Heating / Protect Engine / shuting down the AC system on my 1996 Deville. The car would also miss and Posi/TRAC light would display. The first time it occured I had the Radiator Rodded and Water Pump checked. But the problem didn't go away. My Car guy said possible faulty main Computer or Wiring issue. Happy Selling, Bill Davis

07-08-06, 09:08 PM
There are many simple things to check before you sell it. Is your "car guy" familiar with the Northstar?

07-10-06, 09:20 AM
Well, the problem was something I wouldn't have guessed. I had to have the car towed to my mechanic due to my work hours. He couldn't get to it on Thursday or Friday, so when Saturday came around, I went up to try some of the things you guys talked about. Unfortunately, it was locked up in their bay.

Got a phone call from them this morning and I guess I must have hit something in the road. He said there is a hole in my oil pan big enough to fit a flashlight handle into.

When all is said and done, I'm looking at 750.00. 10 freaking hours labor. Gah!

Still, I obviously have some kind of a coolant issue, with the heating up while idling thingy. But I'll have to tackle that later. At least it wasn't a head gasket!

Thanks everyone for the help!

07-10-06, 09:34 AM
You may have bigger problems than a head gasket if you ran it for very long in that condition.

07-10-06, 10:23 AM
Nope. Probably ran it over 240 degrees for maybe a minute. Didn't hear any knocking or anything.

07-10-06, 04:20 PM
Tempurature is not what I am talking about. If there was a hole in the pan the size of a flashlight handle, then there was no oil. The engine will not run very long with no oil as the bearings will run dry very, very quickly.

07-10-06, 07:25 PM
I would say it's very possible I drove for a good 5 minutes like that. Now, I haven't seen the oil pan yet. I will when I pick the car up on Wednesday. So I don't know how big of a flashlight we're talking about ;-)

Thing is, I don't know exactly when it happened. Obviously I hit something bad, but don't remember hearing it happen. I did park in a gravel parking lot, so maybe a good sized rock got forced up there somehow. I just don't know. All I can tell you is that when I turned the car off, there was no knocking or scary noises of any kind.

07-10-06, 07:43 PM
Nothing makes sense. :hmm: Anything that can put a hole in your oil pan is bound to make enough noise to get your attention, and a hole that size would drain the oil in a New York Minute. The engine would probaly have siezed after about 1 minute with a hole that size in the pan.

07-10-06, 08:03 PM
road trash is deadly at speed. you would certainly hear/feel a hit that punctures the oil pan! check the thread MERL started on his rim problem:


he was traveling quite fast for that hit.

do get a pic and post it, would love to see.

and my guess was it would drain all the oil in a NewYorkSecond - oooohhh