Engine heat spikes with A/C on

Tiny
SKEETER72
  • MEMBER
  • CHEVROLET MONTE CARLO
Just recently during hot (90 degrees and above) with A/C on the guage rises to just over half way on cluster. Will decrease if heater is turned on but that isn't an option in this weather. Just replenished coolant (50/50) in reseviour. Any clues? Only occurs when outside temp is high and A/C is on. Thanks
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Wednesday, June 21st, 2006 AT 1:05 PM

4 Replies

Tiny
SWEEP2WIN
  • MEMBER
You might be leaking pressure from the cooling system. Let the car warm up, turn it off, listen in the engine compartment for a hissing sound to take you right to the leak. If you've never changed the overflow tank cap change that and the thermostat first and try that. If you still run hot change the coolant with some 50/50 premix coolant and make sure you PURGE THE AIR from the cooling system by unscrewing the tiny hex screw. If that still doesn't work then the problem is a plugged radiator. Have it rodded out at a radiator shop.
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Sunday, June 25th, 2006 AT 4:59 PM
Tiny
JOUGH626
  • MEMBER
While the previous post has some good ideas, I would believe your problem lies with a faulty fan. When you engage the a/c, the condenser that sits right in front if your radiator gets hot, really hot. If your not overheating when your a/c is not on, then I would not think your engine cooling system is to blame. Although you did not state what year/model/make you had, chances are that your fan is to blame. Depending on what model you have, you could have a couple different fan setups. With a mechanical fan, make sure the clutch works. Start the engine and let it warm up. Turn on the a/c and let the gauge start to rise into the hot area. If you don't see the fan under the hood start to spin faster, alot faster, that I would check/replace the fan clutch. It you have one or two electric fans, first do everything you would do for the mechanical fan, but instead of checking the clutch, check the fuses, relays, connections, and coolant temp sensors. If those all check out to be fine, then the next step would be to confirm you have 12v at the fan, and if you have the 12v and the fan still does not kick on, then replace the fan. I hope this helps.
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Sunday, June 25th, 2006 AT 5:21 PM
Tiny
SKEETER72
  • MEMBER
Thanks for the info. Sorry I wasn't complete. It's a 1998 Monte Carlo 83K miles. Cooling system was just checked this morning. Heating was blamed on not enough RPMs as the car moved. (That seems odd to me.) About to head out on a trip. If A/C is not used much would this be a major issue needing addressed before heading out? Thanks again. (As you can tell I'm no mechainc! Lol)
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Thursday, June 29th, 2006 AT 5:35 PM
Tiny
SKEETER72
  • MEMBER
Did the testing y'all suggested. The two fan kick in when the A/C comes on when the guage reads half way. When it drops lower the fans kick off. No sounds that resemble a hissing suggesting a leak. I was low on coolant a couple weeks ago and have not seen the guage rise as it did then. If half-3/4 way is tolerable then I'm good (when it's 90+ outside and A/C on). Thermostat? Thanks people.
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Thursday, June 29th, 2006 AT 8:54 PM

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