Overheating

Tiny
IMAQUESTIONMAN
  • MEMBER
  • 1997 CADILLAC DEVILLE
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 170,000 MILES
This vehicle has a normal operating coolant temp of around 200. Why, with the a/c off is it programmed for the fans to not come on till the temp reaches 223? Why don't the fans kick on at 205 0r 210 at the most? Can it be programmed to come on at a lower temp?
Do you
have the same problem?
Yes
No
Monday, March 21st, 2016 AT 8:25 PM

3 Replies

Tiny
CARADIODOC
  • EXPERT
GM fans have been that way for decades and that is considered normal operation. Older Chrysler products turned on at around 210 degrees and off at 198 degrees. GM's turned on at 222 degrees. There's no need to re-engineer what works well.

The radiator cap has a 15 pound pressure relief valve. You raise the boiling point of water by three degrees for every pound of pressure, so you raise its boiling point to 257 degrees.
Was this
answer
helpful?
Yes
No
+1
Monday, March 21st, 2016 AT 8:59 PM
Tiny
IMAQUESTIONMAN
  • MEMBER
Thank you for your reply. I have a hard time understanding the 222 threshold. My car runs great at 192. What is the benefit of letting it get to 222 before turning the fan on. By the time the temperature gets to 222 it's rising faster and faster and engine failure is fast approaching. If the fans fail you don't have much time to react--especially if your in traffic. If the fans were supposed to kick on at 205 and your temperature gauge hit 215 you'd know you'd better get off the freeway fast and shut your engine off. What happens now with my car is I'll be stuck in traffic with the temperature getting into the 240's (now, did the high speed fan kick on at 234 and it's it's just playing catch up to get the temp back down or are the fans not working and "where's a dang exit?" It sounds like GM is saying "Skydiving is fun--Let's wait till we're 200 feet above the ground before we pull the rip cord". Why take a chance?
Was this
answer
helpful?
Yes
No
Thursday, March 24th, 2016 AT 3:51 PM
Tiny
CARADIODOC
  • EXPERT
When I can't think of a logical answer, it is usually because it has something do with lowering emissions a tiny little bit at the potential expense of a few overheated engines. In case you haven't picked up on it, I have very little respect for car designers and even less for the unknowlegeable politicians who make laws the rest of us have follow.

Higher cylinder temperatures promote more complete combustion of fuel, and therefore, lower emissions. Pistons are oval-shaped and grow to fit the cylinders at the temperature they're designed to run at. Running at a lower temperature will greatly increase cylinder wear due to the poorly-fitting pistons. Contaminants in oil won't boil off as easily at lower temperatures resulting in more sludge. You'll actually do more damage through accelerated wear running at 195 than at 220 degrees.

Remember too the fan isn't needed at highway speed. Natural air flow takes care of the radiator. The thermostat sets the operating temperature, and the fan only comes into the picture at very slow speeds or when standing still. The fan on my '88 Grand Caravan turned on very rarely and only on hot summer days during prolonged idle.
Was this
answer
helpful?
Yes
No
Thursday, March 24th, 2016 AT 9:40 PM

Please login or register to post a reply.

Recommended Guides