My 2004 trail blazer registers 210 and climbs to 235 when stopped in traffic. I have changed the sending unit and replaced the thermostat. Any ideas?

Bryan Sanders

Asked by Sep 11, 2014 at 08:43 PM about the 2004 Chevrolet TrailBlazer LS 4WD

Question type: Maintenance & Repair

7 Answers


Poor air flow through the radiator, check for crud in the fins of the radiator, if it is clean then your fan is not kicking in. As this vehicle has an electric clutch you can either replace the clutch and hope that is it or your can take it to a shop and have the unit checked out. Another option is to install a pusher electric fan behind the grill.

2 out of 2 people think this is helpful.
John Carson

Is it summer and are you in city traffic with the A/C on driving on black asphalt? Like good old tennissshoes said, a clean radiator is a happy radiator. Do you have the fan shroud still on over the clutch fan? The next time it starts to get up towards the 235 mark, pull into a parking lot, raise the hood and see of the fan or fans if you have electrical radiator fans, are working and pulling air. If you have duel electrical fans on the radiator, one will start when the A/c is turned on, the other when the engine gets to a preset temp. After 10 years of driving, maybe it's time for a system tune-up and radiator flush? When the truck is cold, see if there is a proper amount of radiator fluid in the over flow tank.

Best Answer
Bryan Sanders

Yes califcarson I have a shroud a round the fan. It is a fan that increases speed with horse power the way I understand it. The next time the temp rises I will check the fan to ensure it's turning.

John Carson

That is a "clutch" fan. It will free rotate but will engague when the temp gets to a set degree. You will hear the fan making a distinctive sound when it is engaged. On start up on cooler mornings and the engine is still cold, look and listen to the fan. Later after driving the the engine is warmed up or hot, check and see if you can hear the difference. Before I replaced the one on my Corvette, it had gone out three times over the course of 40 years. I removed it as it does sap 10 HP when it is running. I went to two pull through electrical fans on my radiator.


As this is a electric fan clutch it will not act as a normal fan clutch, it will free wheel most of the time until it is turned on by the ECM. Just another messed up way to cool an engine and cost you more cash to have it diagnosised and fixed.

John Carson

There may be your problem. You can get a solid fan that runs all the time, just bolt it on. Check the cost, and if it's worth the try, buy it, bolt it on and see what happens. It has worked on cars, trucks, and engines for over 100 years. Your temp sensor for the fan may be bad or have a bad connection. Still do the hearing test on the fan first though. If you can, see if it is working as it should.

John Carson

Is the fan connected to the engine or radiator? On my 69 Corvette, it was not hooked up to anything. It had a spring that expanded with the heat and pushed the clutch pads against the inside of the blade when it go hot. If it rotates, how is it connected electrically? Is there a stationary covering that it is connected to? If so, check the connections for corrosion or broken or hot frayed wires.

1 out of 1 people think this is helpful.

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