When it runs with the heater on blows good hot.

Tiny
ANONYMOUS
  • MEMBER
  • 2002 GMC JIMMY
  • 109,000 MILES
When it runs with the heater on blows good hot air. If you turn fan off it will over heat and has a gauge on dash. Replaced thermostat also didn't help. Can't see any leaks and fan spins while engine off and when it is cold fan is running as soon as you start the vehicle. Any ideas?
Wednesday, March 6th, 2013 AT 6:35 PM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 34,331 POSTS
Check the cooling fins on the radiator to see if they're corroded and crumbling away. It is not giving up the heat to the surrounding air. The heater core is doing that job when you turn the heater fan on. The clue is the radiator hoses will be hot, not cool.
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Wednesday, March 6th, 2013 AT 6:59 PM

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