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Q: overheating problem

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I own a Hummer H2 and it continues to overheat. I have replaced the thermostat, the water pump and the heads. But I still am having the overheating problem. What could this be caused from? Do you have any answers?

A: Thanks for writing in about your Hummer H2....

Thanks for writing in about your Hummer H2. Let's cover the basics of diagnosing a overheating issue. First, verify the actual temperature at the thermostat housing. Cooling system (and cap) has probably been pressure tested by now. If it tends to overheat in stop-and-go traffic, but not at cruising speeds, then it's an airflow issue.

Check the fan clutch, shrouds in place, and look for debris blocking the condenser/radiator. I don't know your mileage, but both the belt and tensioner should have been replaced by this time. If it is overheating at cruising speed, the radiator should be checked for restriction in flow. Have this checked in person by a trained mechanic in order to diagnose the overheating issue and move forward with repairs.

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