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Ted the technician
Ted the technician, ASE Certified Technician
Category: Chevy
Satisfied Customers: 122
Experience:  ASE certified technician, Former GM master tech, Former Lexus Master Diagnostic specialist,
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GMC sierra 1500: V8..5.3 liter..The engine temp has been 40 degrees

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I have a GMC Sierra1500 V8 5.3 liter. The engine temp has been 40 degrees lower than normal. The heat output in the truck feels low also. What could cause the engine to run at a lower temp and is this harmful to the engine itself?

Hi, I'm Ted and I will assist you.


The most likely cause of running cool is a thermostat that is stuck open. This will keep the coolant flowing all the time and not allow the engine to get to full operating temperature. This will also cause the heat not to get very warm.


This running cool is not good for the engine. It will lower your gas mileage. and cause excess carbon in the engine and possibly damage the catalytic convertor.


I would have the thermostat replaced and have the coolant flushed.

Ted the technician and 8 other Chevy Specialists are ready to help you
Customer: replied 7 years ago.
Is changing the thermostat on this truck a difficult operation or can a diyer with a mechanical backround in carpentry be up to the task

Its not a real hard job. The thermostat and housing are replaced together. The part is around $25.00 or less and it takes about a half hour to an hour to do. Just make sure you use a quality unit like from Stant of a GM part. Not some cheap autozone part. I have had nothing but trouble with them.


Replacement (4.8L, 5.3L, and 6.0L Engines)

Removal Procedure

Important: The thermostat is not serviceable separately. The water pump inlet and thermostat must be replaced as an assembly.

  1. Remove the radiator outlet hose.
  2. Remove the water pump inlet bolts.
  3. Remove the water pump inlet and thermostat from the water pump.

Installation Procedure

  1. Install the thermostat and thermostat housing to the water pump. Notice: Refer to Fastener Notice in Service Precautions.
  2. Install the thermostat housing bolts. Tighten the bolts to 15 Nm (11 ft. lbs.) .
  3. Install the radiator outlet hose.




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