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90 sierra running hot?


94HeavyChevy
06-01-2009, 05:04 PM
My buddy has a 1990 GMC sierra and it is running hot. Coolant is new and the fan is working. he also said the thermostat was fairly new. what could be the problem here?? I cant see the thermostat to tell if it is stuck or not? any help would be very appreciated

2000CAYukon
06-03-2009, 10:46 AM
Is it running hot at idle (i.e. stoplights) or is it running hot when driving?

I have seen new tstats stick so that has to be checked (remove it and put it in boiling water to make sure it opens).

At idle, fan clutch could be worn. Check for air flow blockage at the a/c condensor and radiator.

Water pumps can wear out, radiator can also be clogged.

//2000CAYukon

94HeavyChevy
06-03-2009, 06:46 PM
ya it is really just when he is stopped at stop lights or in traffic it gets 75% of the way on the meter but then when he gets going it drops. ill tell him to check those things. thank you for your help

2000CAYukon
06-04-2009, 04:56 PM
I would replace the fan clutch.

//2000CAYukon

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