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Q: My 2004 Chevy Silverado is having cooling system problems

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The truck isn't blowing hot air and the truck is over heating I thought it was the thermostats but after checking those they both open and close the way they should it seems what else could be wrong? the pump and radiator isn't leaking and seem to be working right don't know where to go from their

My car has 160000 miles.
My car has an automatic transmission.

Hi there:

On a 2004 Silverado 6.6L Diesel there is a heater hose bypass valve that opens when the heater is activated. Sometimes this component can become stuck due to corrosion inside the coolant lines or a sensor that has either become unplugged or has an electrical short. If the bypass is not working correctly, it could be the source of your overheating and heater issue. However, there are a few other problems including air bubbles in the cooling lines or other mechanical part defects that should be inspected by a professional mechanic for overheating issues.

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