Mechanics

CHEVY TRUCK OVERHEATS

1994 Chevrolet Silverado • V8 4WD Automatic • 233,000 miles

I have a 1994 chevy 1500 pickup - 350 motor that overheats. I've replaced the radiator (was leaking), water pump, thermostat and fan clutch. The motor only overheats after the operating temperature has been reached then you accelerate to 55mph. When the overheating starts the heater starts to blow cool air into the cab. I also replaced the temperature gauge with an after market, to watch the thermostat (180 degree thermostat). What else needs to be replaced?
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Mmentjes
December 21, 2010.




Overheating is a boil-over. How hot does it get? Does the overflow bottle fill up? I know your fan is belt driven, but, some of the electrical fans won't even kick on till 220 0r better.

JDL
Dec 21, 2010.
Maybe air in the system or combustion gases are heating the coolant?

JDL
Dec 21, 2010.
Sounds like you probably got it too hot and blew a head gasket. They can run some chemical tests to check for that.

Wrenchtech
Dec 21, 2010.
JDL - The temp climbs to over 250 and fills the over flow bottle, then flows out the top of the overflow bottle on to the exhaust.

Wrenchtech - I also believe that the head gasket may be next on my list - I've dropped it off at a local mechanic to verify.

The puzzling piece of this is why would the cab heat start to blow out cool air when the motor is overheating? The cab temp is set to hot as here in MN the temp is cooler (relatively speaking).
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Tiny
Mmentjes
Dec 22, 2010.
Losing your heat is a normal symptom because hot gases start to displace the hot coolant in the system and without liquid, you have no heat. This is why your temp gauge will frequently read incorrectly also.

Wrenchtech
Dec 22, 2010.

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