: 96 Deville running hot



57ringo
12-18-05, 01:58 PM
We've had a 96 Deville since 97. It NEVER ran over 205 on a hot summer day even in heavy traffic. Last year it started running hot and up to 225 in traffic with AC not on but most of the time on the interstate from 203-210. I changed the thermostat and water pump with new GM parts. It still runs the same temp. Yesterday was 26 here and it still ran 206-212 driving 50 MPH on a snow packed road. The coolant level stays full. There is no leaks. the Cadi dealer I talked to thought it could be a radiator problem. When I replaced the water pump, the inside of the coolant system was very clean and the pump came out fine so that makes me think the rest of the coolant system is clean. I've heard people say not to worry about running that hot but if it didn't do that from 96-2003, something is not right with it. Any others ran into this problem?

Ranger
12-18-05, 05:03 PM
Not sure what temps you are talking about. 206-212 is normal operating temp. 225 is on the warm side as that is where the cooling fans turn on. Have you checked the purge line to be sure it is not plugged?

57ringo
12-18-05, 05:10 PM
Are you talking about the line to the tank with the radiator cap? It didn't make any difference before I changed the water pump or after. I didn't have any problem refilling the coolant. I understand that up to 212 might be ok but why didn't it do it the first several years we had it? Something has changed to cause this. When the AC is on, the fans are on and it still gets hotter than it used to. When it got up to 227 once, it was set on economy so the fans were not on and I was in traffic.

99DeVilleElegance
12-18-05, 07:26 PM
I have 1998 DeVille and 1999 DeVille D'Elegance (same cars but different trim level).
I bought 1999 with 6400 miles, today it has about 10000. It keeps temperature 194...196 on the highway and 199...201 on the street all year long (I live in Atlanta and summer here is HOT).
The second (1998 Deville) car was purchased with 11500 miles and today it has about 25000. From the day one temperature on the highway 198...208, on the street or in light traffic it immediately jumps to 208...212, in heavy traffic I've seen 228. I've checked everything, changed coolant, still the same.
I think the problem is in thermostat, more specifically in temperature when it is fully opens. Northstar thermostat should be fully opened at 180 degrees, but you never know (even with brand new) how it was made. One can open at 180, another at 195 and and both will work, but engine temperature will be different.

57ringo
12-18-05, 07:35 PM
I wonder if the temp sensor is giving a faulty reading. Since the temperature reading was similar the first few years and not now, and changing the water pump and thermostat didn't change a thing, maybe the sensor is bad. I've been going to take a few readings with my infrared temp gun to see how far off the gauge might be.

Ranger
12-18-05, 08:47 PM
Are you talking about the line to the tank with the radiator cap? It didn't make any difference before I changed the water pump or after. I didn't have any problem refilling the coolant. I understand that up to 212 might be ok but why didn't it do it the first several years we had it? Something has changed to cause this. When the AC is on, the fans are on and it still gets hotter than it used to. When it got up to 227 once, it was set on economy so the fans were not on and I was in traffic.
The purge line is the 3/8" line that runs from the pump to the surge tank. If it is plugged, it cannot purge air and will run hot and may overheat. Just loosen the clamp with the engine running (cold so as not to scald yourself) and see if there is flow. If so, quickly plug it back on and tighten the clamp.

mcowden
12-18-05, 08:49 PM
I think you're worried about nothing. If it gets up to 240 while you're moving, there could be a problem. Until then, just maintain the cooling system the way it's supposed to be maintained and stop worrying about it. Is there anything obstructing the radiator? Have you cleaned the fins before?

STYES
12-18-05, 10:01 PM
Have you been using the coolant tabs/bars leak? I own a 96 DeVille as well but it only has 61K on it. The damned digital dash has got me to leave the "info" on the tach, because otherwise it doesn't have one per se. I will check to see where mine runs at and let you know as soon as I find out.

57ringo
12-18-05, 10:44 PM
I'm not just going to let it go. I have worked on many engines and know when something changes like this, something is wrong. If it was fine for several years and now is heating up, I'm going to worry about it. The fins look good and it hasn't leaked so I haven't put any stop leak, tabs or any other stuff to clog the system. I will check the purge line too.
Thanks,
Pat

eldorado1
12-18-05, 10:52 PM
The bars leak are a maintenance item. It's in the manual. :thumbsup:

57ringo
12-18-05, 10:56 PM
I was told by a dealer that GM puts a couple tabs in every new vehicle they sell in case there is some small leak, it will be taken care of. It wont help clean a system.

57ringo
12-18-05, 11:29 PM
Here's what another guy posted on another forum about this same type of problem:

"There is also a STRONG possibility that you have a radiator problem such as a residue buildup at the bottom of the radiator vanes and partially up towards the center of the radiator OR you could have a problem with the lower and middle coolant chambers of the radiator that are collapsing when hot thus restricting the coolant flow"

Have you guys heard this before?

Ranger
12-19-05, 11:24 AM
Anything is possible. Have you flushed the radiator?

57ringo
12-19-05, 11:28 AM
I have not flushed it. I just drove it this morning, 19 degrees weather and it got up to 212. I shot it with my infrared thermometer and at the thermostat was 201, radiator hoses 78-175 so I would think the radiator was not obstructed. Where is the temp sensor located? I don't think I'm getting a true reading with the sensor.

57ringo
12-19-05, 04:36 PM
Ranger, I took the hose off and coolant was flowing through it. I tested the cap and it was ok too.

Ranger
12-19-05, 08:40 PM
Don't quote me here but I think the temp sensor is in the back (drivers side) of the right bank (rear) head. That said, I really think you are chasing a ghost. Those temps are perfectly normal. My '97 Deville ran a consistant 206 in the summer, even in 95 degree weather, and 213-216 in the winter (the colder it was outside, the warmer it ran). Sold it in Oct with 107K and never a problem.

eldorado1
12-19-05, 08:46 PM
General things to check-

Move water pump belt tensioner. Lubricate if binding
Check front of radiator for road spray, leaves, debris, mud, dead cats, etc...

57ringo
12-19-05, 08:48 PM
But why would the temp reading be similar for years and now heat up? Something has changed.

57ringo
12-19-05, 08:57 PM
I installed a new tensioner and belt when I put the new water pump in, they are ok, and the radiator is clean.

Ranger
12-19-05, 10:28 PM
But why would the temp reading be similar for years and now heat up? Something has changed.
One posibility is that you had a "problem" for years and didn't know it. That being that the stat was hanging open, causing the car to run cooler. Now with a new stat, it is running where it is supposed to. Just a shot in the dark here, but I can assure you that the temps you mention (212 @ 19 ambient) are normal.

57ringo
12-19-05, 10:32 PM
but when it's hot outside, I've seen it 217-227. It never did get over 205 for years.

Ranger
12-19-05, 10:49 PM
That is a tad hotter than I have ever seen on mine. Not sure what to tell you there other than the basics (pressure cap, purge line, tensioner, flush radiator) which it sounds like you have covered.

EDIT: On second thought, how about dead bugs etc, clogging the radiator fins? Have you tried blowing and flushing them out?

57ringo
12-20-05, 08:13 AM
I has the normal few bugs in it but not very bad. Yesterday was 19 outside when I was driving. The inlet hose to the radiator was 175 and outlet 75 according to my infrared thermometer. That tells me that the radiatior is cooling especially in this cold weather. The reading at the thermostat housing was 201. I need to check where the sensor is, maybe it's faulty. It seems like if I have not too hot coolant entering the radiator and it's cool leaving, and 201 at the thermostat housing, the sensor is giving me a wrong reading.