Cadillac Owners Forum banner

1 - 10 of 10 Posts

·
1995 ETC
Joined
·
8 Posts
Discussion Starter #1
Thank you for the question and replys. I have had a question bugging me now for several weeks, regarding my cooling system. I have a 95 ETC with less than 70K miles. I am really enjoying the car. However my coolant temp will fluctuate from 179 to 235 with little provocation, (well climbing a 4200 ft. pass with the ambient temp about 90 degrees, A/C running). As soon as I drop over the top of the pass, and take the load off, the temp comes right down to 180-190. 235 degrees seems too hot to me, but after coming to know the high speed of the fans doesn't kick in until 236, I guess I am just over reacting. If I was reading a dummied down analog gauge, I probably would not even notice the wide temperature variations. (Well I probably would). I have noticed that ambient temperature, makes a big difference in how my cooling system responds. Does this all sound normal? I suppose I could just hit the "display off" button??
 

·
Super Moderator
2010 DTS
Joined
·
87,306 Posts
Moved from temperature thread in the Deville forum.

Temperature climbing under a load as you describe is a symptom of a HG failure. Do a block test to check for exhaust gasses in the surge tank. That will confirm or rule out the HG.
 

·
1995 ETC
Joined
·
8 Posts
Discussion Starter #3
Moved from temperature thread in the Deville forum.

Temperature climbing under a load as you describe is a symptom of a HG failure. Do a block test to check for exhaust gasses in the surge tank. That will confirm or rule out the HG.
Thank you for your reply. Yes, a block test is next. Truthfully, I have been putting it off. If I verify a HG issue, then I have to do something about it.
 

·
Registered
2011 DTS Premium w/1SD | 1999 Deville Base (RIP @179K Miles)
Joined
·
453 Posts
How fast were you going up that hill?

I have a 2011 DTS with the Northstar engine. Last week I drove up Whiteface mountain (4800ft) memorial highway going between 20-30MPH. When I reached the top, my coolant temp was at 230/233 or the 1 O'clock mark on the gauge. After a few minutes with the fan on low speed, the temp went back down to normal. This is one of the ~3 times I've seen my car get that hot since I bought it 2.5 years ago.

I think 235 is normal if it only happens going slowly up a very big hill in hot weather. In 100 degree traffic with the A/C on, my temp gauge stays in the middle.
 

·
1995 ETC
Joined
·
8 Posts
Discussion Starter #5
How fast were you going up that hill?

I have a 2011 DTS with the Northstar engine. Last week I drove up Whiteface mountain (4800ft) memorial highway going between 20-30MPH. When I reached the top, my coolant temp was at 230/233 or the 1 O'clock mark on the gauge. After a few minutes with the fan on low speed, the temp went back down to normal. This is one of the ~3 times I've seen my car get that hot since I bought it 2.5 years ago.

I think 235 is normal if it only happens going slowly up a very big hill in hot weather. In 100 degree traffic with the A/C on, my temp gauge stays in the middle.
I think at the time I was just going the speed limit, 60mph.
 

·
1995 ETC
Joined
·
8 Posts
Discussion Starter #6
Thanks guys for your interest and replys. When I purchased the car about a year ago, the first thing I did was flush out the old orange coolant with lots of distilled water, (time consuming). The old stuff looked pretty bad, which made first start thinking HG issues ahead. I replaced it with the same color coolant. Normally the car runs between 197 and 215. On a cool day, it runs cool. I have not verified the HG issue yet with a block test, but assuming I do have compromised head gaskets, does anyone know of a shop, or individual, in the Pacific Northwest, that has a good reputation for doing the repairs? I live dead center in Washington State. Thanks.
 

·
1995 ETC
Joined
·
8 Posts
Discussion Starter #7
An update on my heating questions. I did a block test and was able to replicate the test with no color changes three times in a row. I don't think I have head bolt issues after all. But while doing the test, I noticed my engine temp would vacillate between 203 and 225 (when the fans kicked on). Today I replaced the thermostat, (180 degrees), thinking maybe I had a stuck thermostat, and verified the upper small line to the overflow tank was clear. Same results, while idling under no load, (and no air movement), the temp would run the gambit between 210 and 225, then back down again to 208-210, then up again. I am guessing with no forward motion, that these temps are reasonable, perhaps normal. I think I read somewhere that normal operating temperatures are usually in the 208 to 217 range. Should I be concerned, or just drive it and watch that the temps don't exceed 240, (which strikes me as way too hot)?
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
70,388 Posts
With no A/C compressor function set it is perfectly normal for the coolant temp to rise to about 224 degrees before the fans go to SLOW. Fans go to FAST at 236. The engine cools to 213, fans shut off, the cycle repeats. Slow/stopped speeds. Over about 25 - 30 fans don't run. With an A/C or DEFROST function set the fans run in SLOW all the time to insure airflow through the A/C condenser.

A Northstar with a good cooling system will run all day at 188 - 205 degrees. Probably 190 - 195 at highway speeds. Slow down and stop, temp rises.Normal. Climb a mountain,. temp rises. Normal. Go down the mountain, temp drops. Normal.

Your engine uses the same temp sensor as mine, so the tick marks on my gauge correspond to yours. Note the yellow and red fan temps. DO NOT install a low temp thermostat. The indistinct white dot at about 160 degrees is emissions loop change temp - run the engine near that temp and you get all sorts of odd problems.

The Northstar was designed and tested to run for 50 miles with NO coolant. Overheat occurs at about 270 degrees and the engine goes into Camel Mode.

Temp gauge - my numbers.jpg
 

·
1995 ETC
Joined
·
8 Posts
Discussion Starter #9
Sub, Thank you for taking your time to replay and explain the cooling temps in greater detail. Looks like my system is running as it should. I did not know that I could turn the fans on with the defrost setting. My A/C refrigerant had leaked out, so I was not able to turn my fans on during the above mentioned tests (or so I thought). I took the car in today to determine the cause of the A/C leak, (because I wanted to be able to activate those fans). Looks like a new compressor will be installed the first of next week. I really appreciate all the time you take on this site to help out those of us that want to keep these nice cars on the road. This site is a tremendous resource. Thanks again.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
70,388 Posts
FWIW the Northstar cooling fan sequencing and temperature settings were modified in the 2005 or 2006 model years. A Northstar owner needs to know which fan programming he/she is dealing with.

All (FWD) Northstars from 2005 back were about the same as my description in Post #6 - later FWD, AWD, and RWD models are different and their fan sequencing is described in the GM/Cadillac service manuals, cooling system description and operation. www.alldatadiy.com or www.helminc.com.

Also, the Northstar shuts off the fuel injectors during extended coastdown, so that factors into cooldown in mountain driving. My STS will drop 20 degrees while coasting down the west side of Panorama Mountain entering the Shenandoah Valley. Probably a lot more if out in the Rockies, etc.. If you run your FWD Northstar up to the speed limiter (112 for VIN Y, 130 for VIN 9, 149+ for the few Z-cars) and flip you foot off the gas pedal for coastdown after a second or so you'll hear a !! BLUP !!! exhaust fart as the injectors cut off.
 
1 - 10 of 10 Posts
Top