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Overheating

Tiny
AMONKEY
  • MEMBER
  • 1987 CHEVROLET CELEBRITY
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 66,890 MILES
Car overheats and stalls and the temp light never comes on to warn you. The cooling fan never comes on unless you set to heat/defrost. Replaced fan relay and temp sensors near the thermostat housing. 1987 chevy celebrity 2.5 l. What else can it be?
Saturday, April 9th, 2011 AT 2:00 PM

4 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
How do you know it's overheating? The radiator fan is likely turning on in response to switching to defrost. The air conditioning runs in defrost mode and that is direct-wired to the fan. That proves the fan and relay are working.
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Saturday, April 9th, 2011 AT 2:24 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
What is the actual temp? Some fans won't come on till about 220degreesf. Check for applicable mil codes, you can check those yourself. You place a jumper wire between A & B terminals at the datalink connector. Turn key till the dash lites come on, no further. The mil starts flashing, you count the flashes to get the codes. Your looking for two digit codes.

The thermostat is a possible issue for overheating? If you unplug the cts, the fan may run, key on. Sometimes when you use the jumper to access codes, the fan will run.
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Saturday, April 9th, 2011 AT 2:32 PM
Tiny
AMONKEY
  • MEMBER
  • 2 POSTS
Thanks for the responses. If you leave the car idoling long enough, the radiator boils and the car stalls out. It will not run again until you have let it sit for about 10 to 15 minutes, depending on the temperatur and the type of driving. Around town you can count on it overheating in about 15 minutes of run time. On the highway, Ive been as much as 145 miles with no problems, but it was about 45 degrees outside.
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Monday, April 11th, 2011 AT 1:18 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
We gave you a lot of info, did you check anything? The coolant temp sensor can have an effect on when the fan runs. I've already asked, what about trouble codes? Replace the thermostat, if in doubt.
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Monday, April 11th, 2011 AT 2:46 PM

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