my 2004 4.3 engine is constantly overheating

Asked by thomasrb Jul 30, 2016 at 10:56 AM about the 2004 Chevrolet S-10 LS Crew Cab 4WD

Question type: Maintenance & Repair

When the truck idols, its fine. when driving the temp needle goes above
210. heat comes down to the floor board that almost scalds your feet
through your shoes. if i turn on the AC temp really shoots up while driving.
Fan is strong, replaced coolant sensor, thermostat, flushed radiator system
of red rust, and checked for leaks. I know the pump is working becouse
when i crank it with the cap off it sucks the coolant on down. cleaned out
around the grill and radiator. evn checked to make sure the oil and coolant
were not mixing. what else is thier to do? im lost!!

3 Answers
101,715

KenF answered 7 years ago

Try checking your water pump again, squeeze the upper radiator hose when revving the engine, you should feel the pressure build. It may have lost some efficiency from wear. Another test is for hydrocarbons, a product like Napa's "Block Tester" will let you know if combustion gases are causing coolant to overheat. Not all head gasket leaks result in oil/coolant mixing. If you have hydrocarbons present you have a head gasket issue.

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thomasrb answered 7 years ago

and what would be an easy way to check and make sure the radiator is cooling and not leaking internally? any ideas?

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101,715

KenF answered 7 years ago

It wouldn't leak internally but it may be clogged up with hard deposits with a loss of efficiency. You might still have enough "flow" to get by with a typical garden-hose flush but not good enough to prevent overheating. Also make sure after any work you get all the trapped air out of the system.

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