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Joshua, GM Performance Tuner
Category: Chevy
Satisfied Customers: 129
Experience:  Extensive Training in GM engine management systems & performance Tuning.
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2001 gmc yukon: 5.3 is overheating..Replaced thermostat

Resolved Question:

2001 gmc yukon 5.3 is overheating. Replaced thermostat and still overheating.
Submitted: 9 years ago.
Category: Chevy
Expert:  Joshua replied 9 years ago.

its somewhat common that the coolant temp sensor goes bad and registers a high temp value to the gauge, But if it is visibly getting hot then lets look at the major causes:

bad water pump, doesn't necessarily leak when its on its way out.

bad stat ( which you replaced)

plugged radiator

Let me know if I can be of further assistance

Joshua and 4 other Chevy Specialists are ready to help you
Customer: replied 9 years ago.
Reply to Joshua's Post: I just replaced the fill cap and didn't solve the problem. This problem has been going on for a while ,but off and on. But now it just stays hot. Yesterday I rushed home as it was overheating and barely got home. As I was approaching my drive way the engine was wanting to shut down. Today the engine runs fine, but was still getting hot. After I changed the thermostat and added coolant, I noticed that the coolant in the filler tank wasn't going down. So I assumed it was a flow problem. By the way, the water in the filler tank was either bubbling or boiling for a few seconds after I shut the engine off.

Expert:  Joshua replied 9 years ago.
Bubbling can mean a bad head gasket, air pushing thru the gasket area making the bubbles.

if its not flowing, it could be a bad water pump.

if the radiator is plugged it will not allow any or very little coolant to flow, thus it wont cool the vehicle properly.

Customer: replied 9 years ago.
Just replaced the water pump and still overheats.

The radiator flows good. I placed the water hose in one outlet and water flows freely out the other end. One thing I noticed is that with the new water pump the water bubbles a lot continuously in the filler tank. The bubbles come out of the hose that connects to the water pump from the filler tank.

There's no water in the oil to indicate a blown head gasket.
Expert:  Joshua replied 9 years ago.
If its a relatively small leak, it will push more air out of the gasket, then it will draw in. that is the only source the bubbles could be coming from.