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Discussion Starter #1
I have a 97 STS, ive replaced the radiator,water pump,surge tank, and the thermo.. It will run fine between 190-205, then will jump to 228, then in 30 seconds will be back at 196. Today i was driving i accelerated to about 5000 rpms to get on the high way due to exccesive speeders, when i looked at the digital it started to climb, 240,250,262 before i could pull off, coolant was splashing out of the overflow, and after the coolant stopped, it smoked for awhile. There was barely any coolant left. I also noticed my transmission fluid was leaking by the radiator. Im loosing coolant somewhere, but i ahve no signs of a blown head gasket, the car runs great besides the overheating problem. When it got upto 262* a warning was displayed on digital "turning off ac compressor to advoid damage, however the "hot idle" warning never came on which comes on at 248*, so is my car really getting that hot??? Or do i have a faulty coolant sensor, also does the sensor control anything else besides only displaying the coolant temp, or could this be my problem? Also the air hisses when i turn it off or switch to low, could my air be the problem, when off, it seems to not get as hot.
Thanks

Ive read all of the threads on overheating, but most when its overheated it only goes hotter, not lower.. or up & down. As there supposedly is no such thing as a car that overheats sometimes...
 

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White Diamond '03 DHS (with DTS floor shift)
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If you read the overheating threads, then you know what the usual culprits are. The 2 you haven't checked are the purge line and the cap. If they are OK, get a cylinder pressure test done or have the coolant tested for exhaust gases.
 

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Discussion Starter #4
What is the purge line, and are you talking about the overflow tank cap? I replaced it with an OEM from Cadillac, however when it was at 228 one time, i could here a slight hiss from the cap, but i no longer hear it.
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94 ETC,97 STS
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chasetoys; said:
As there supposedly is no such thing as a car that overheats sometimes...
????????????? Most cars only overheat sometimes. !!!!!!!!!!!!!!

Ranger gave you the best advice...

Get an exhaust test done at a radiator shop.
 

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White Diamond '03 DHS (with DTS floor shift)
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Do a search for purge line. I have described it many times. It is a simple check.
 

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Discussion Starter #7
Hey Ranger, also can you tell me where the coolant sensor is located on this engine, in my repair book, it only shows a newer engine, and things have been moved around, i cant find it. Thanks
 

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White Diamond '03 DHS (with DTS floor shift)
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I think it is in the end of the rear head, drivers side, but don't quote me on that.
 

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2007 CTS White Diamond - 1997 Deville Silver Mist
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Hey Ranger, also can you tell me where the coolant sensor is located on this engine, in my repair book, it only shows a newer engine, and things have been moved around, i cant find it. Thanks
You mentioned something about a faulty Coolant Temperature Sensor. It sounds to me like your car is definitely overheating. Coolant wouldn't be splashing out of the Surge Tank and you wouldn't have a loss of coolant if you weren't overheating. Unfortunately, I believe one of the signs of a blown head gasket is overheating upon heavy acceleration. Do the coolant exhaust test that was described above to make sure.
 

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Discussion Starter #11
Hey ive searched the threads for purge line but cant seem to find it? Its located on the water pump and is about 3/8 does it run twards the dash of the car? I have a 3/8 running from water pump twards front of car with some type of a green hose clamp on it?
 

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Discussion Starter #12
Hey i checked the purge line, flow was steady however, i checked the crossover hose from the radiator on the pass side to the other side of the car and was just a trickle? Should there also be good flow there, or is this normal? I think i might have clog b/c when i replaced surge tank i had alot of sludge in there, ive already replaced radiator however, so i know its not clogged? If the trickle is suppose to have a larger flow, where might the clog be if its that. Thanks
 

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White Diamond '03 DHS (with DTS floor shift)
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The purge line runs from the water pump to the surge tank. It is a 3/8" line. I think on the '97 it runs along the inboard side of the cam cover under the silver beauty cover. Flow will increase with RPM. I do not know what "crossover hose" you are talking about.
 

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Discussion Starter #14
Its the think tube that runs along the radiator at the top, runs from radiatr over, i thought it was called the water crossover. Not sure, anyways there was jsut a trickle not a full flow like the purge line was. Thanks
 

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White Diamond '03 DHS (with DTS floor shift)
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The "crossover" is the manifold on the back (drivers side) of the engine that allow coolant to crossover from one head to the other since the Northstar has a "dry" intake manifold which would normally carry coolant from one head to the other. I still can't figure out what line you are talking about. Your are saying that it definitely has coolant in it? Is it rubber or steel? Hot or cold? Where exactly does it run from and to?
 

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Discussion Starter #17
Sorry, its the upper radiator hose that has trickle? Should there be more flow, such as the purge line.? Thanks
 

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White Diamond '03 DHS (with DTS floor shift)
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I had to stop and think about this for a second. I was going to say it should have a good flow, but with the engine cold (thermostat closed) I would not expect much flow through the radiator. The hose should be hot when at normal operating temperature.
 

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Sedan de Ville, CTS
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I will be glad when either of these happens:

All of our cell phones can send video.

or

GM has re-done the Northstars in such a way that overheating will not be as consequential. I believe they made progress from 2000 on, but I feel sorry for people with earlier Northstars. That is the only reason I sold my 97 with 27k miles. I was afraid that IF I had a problem, I would then be a proud owner of 4000 lbs of plastic and some metal.
 
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