I have a 99 suburban overheating, i have changed the thermostat,fan clutch, flushed the radiator, still the same thing, it's a 7.4 with 150,000 miles, any ideas ?
Did you flush the entire cooling system, engine and all?
If not you need to. But from what you said you did. So we go one to the next thing, thermostat. It can still be bad, try running it without the stat. you could have a bad one.
Then there is always the dreaded head gasket. Is it loosing fluid?
Unless you have owned this from new someone may have put some type of sealant in the system trying to fix a leak and if not done properly that can plug cooling passages.
Another thought..... Is the radiator the original or has it been replaced. The cooling system may not be flowing completely through the radiator, thus returning still hot.
Another thought.....the transmission could be running hot and overheating the cooling system, however the 7.4 2500's should have a tranny cooler///
Ya, normally overheating at low/no speeds is an airflow issue. And overheating at 40+ is a volume/capacity issue. That's assuming everything else (pump, stat, ect) is in working order.
I didn't flush the engine, it will start running hot just sitting still or in traffic, if i stay out of traffic & driving, it's fine, any ideas ? How do you flush the engine ?
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