[AT] HELP I'm stumped. truck problems, overheating

Darrell Ratliff dbigdog at columbus.rr.com
Sat Aug 29 12:33:34 PDT 2015


Check the fan clutch.


From: charlie hill 
Sent: Saturday, August 29, 2015 3:25 PM
To: Antique tractor email discussion group 
Subject: [AT] HELP I'm stumped. truck problems, overheating

Ok guys, my 06 GMC 5.3 liter engine started
overheating when first started up.  It would get up
to about 220 or 230 degrees.  I could turn the heater
on and get NO hot air flow.  Then all of a sudden
it would start to cool and the heater would blow hot air.
OK easy, bad thermostat.

I go and get a new t-stat and put it in.  Same problem except
worse.  Now it gets up close to 250 before it starts to cool down.
I took the old thermostat in the house and put it in a pot of water on
the stove with a cooking thermometer in it.  It opens and closes as it
should.

Anyone got an idea what is going on?  For those not familiar with
the 5.3 GM engines the t-stat is not in the intake like GM motors of
old. It's in the front of the water pump housing so it should not be
prone to having an airlock at the thermostat.   I see no sign
of bubbling in the coolant.  I'm not loosing an appreciable amount of
coolant and there is no sign of coolant it the water or out the exhaust.
I did however have to add some coolant a few weeks ago which is unusual
and I have smelled an odor that smells like a coolant leak.  It's the same
odor you smell in the cab when a heater core is leaking.  But I haven't 
found
any sign of a leak anywhere.

Right now I'm sitting at home with both of my vehicles not running.  I need
answers quick.

Thanks

Charlie 

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