[Michael123789]

Hi all. I've got my eldorado overheat problem 90% solved, found a clogged line - replaced, radiator and heater core - replaced, thermostat - replaced, cracked reservoir/overflow tank - replaced, block test comes back negative for head gasket issue, but she's still overheating at stoplights/in traffic. But when she gets moving, even coasting she cools down which makes me think its possibly the fans in front of the radiator. Should they start spinning as soon as i start the car, or is there some kind of condition that makes them go on/go off? Is it common for the fans to go, or is there some kind of relay or electrical component i should look at before plunking down $130 on new fans? Any advice would be appreciated.

 

[Submariner409]

Welcome to CF !!!

If you don't have an A/C compressor function set then fans go to SLOW at 224 degrees and FAST at 236. They do not run all the time or over 30 mph or so. If the fans turn on at 224 the engine cools to 213, fans turn off, the cycle repeats - town or suburban traffic conditions.

With any A/C or DEFROST function set the fans run in SLOW all the time to insure airflow through the condenser in front of the radiator.

The coolant purge line must be clean and flow a small steady stream at idle. It goes from the hollow bolt/nipple on the water crossover over to the coolant surge tank. The hollow bolt/nipple tends to clog, especially if you use the no-longer-recommended coolant supplement tablets - they clog all sorts of stuff. If you have a coolant heated throttlebody, bypass it - from the bolt/nipple straight to the surge tank. The water crossover drawing is post-2000 but you get the idea.

The fans have their own maxi-fuses and relays in the underhood fuse boxes.

Google "cadillac forums 1997 northstar cooling fan operation" or something close.

ALL of this is explained in the GM/Cadillac/Helm service manuals. Either find a used set on eBay or subscribe the car to www.alldatadiy.com - the online GM service manuals plus a LOT more.

Here's your cooling fan schematic.

 

[Michael123789]

Welcome to CF !!!

If you don't have an A/C compressor function set then fans go to SLOW at 224 degrees and FAST at 236. They do not run all the time or over 30 mph or so. If the fans turn on at 224 the engine cools to 213, fans turn off, the cycle repeats - town or suburban traffic conditions.

The fans have their own maxi-fuses and relays in the underhood fuse boxes.

Google "cadillac forums 1997 northstar cooling fan operation" or something close.

Here's your cooling fan schematic.

View attachment 578968

You are awesome, thank you!

 

[Michael123789]

Follow up question after reading your reply. I have an error that refrigerant is low, ac compressor is turned off. Could that be affecting fan operation with the schematic showing routing through the ac compressor?

 

[Submariner409]

No - when the compressor is dead the clutch does not engage and the serpentine belt operates normally. Fans are automatically set to SLOW in the PCM when some A/C function is called for - not only when the compressor actually runs (clutch kicks in).

 

[maeng9981]

When you say it's overheating how hot does it get? A lot of people chase a non-issue on these cars (and somehow say it's because of head gaskets), gauge moving slightly past the middle is normal operation for these.

 

[Michael123789]

When you say it's overheating how hot does it get? A lot of people chase a non-issue on these cars (and somehow say it's because of head gaskets), gauge moving slightly past the middle is normal operation for these.

She used to get very hot, the gauge would go past middle and head fast for the red zone. I was told once that happens a few times you have to replace your thermostat because it affects the spring. Since the last round of fixes, I haven't let her get much hotter than a little past center before either pulling over and resting her for an hour, or I get her onto some open road and it goes back down to center. Been dealing with this for so long you're right that i'm probably a bit paranoid. I watch the temp gauge way more than i watch the speedometer

 

[Submariner409]

You were seriously misinformed about the thermostat and an overly warm engine. "Overheat" does not occur until over 270 degrees and the Northstar was designed and tested to go into "camel mode" with total loss of coolant and then run for 50 miles.

"A little past center" is nothing to worry about. Past the next tick mark is cause for caution.

Your tick marks correspond to those on my gauge - both engines use the same temp sender. Anything over 236 degrees is cause for worry. Otherwise, drive the car.