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2004 gmc envoy_slt_xuv
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Well, flushed the Trans, with new fluid.. Still running hot, after a few fast passes on the eway,, 215 in about 10 minutes. I did stop as soon as I got off the e-way and inspected the catalytic converter,,, It was not cherry red, but the welds were before and after the converter where glowing red??
 

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2004 chevy trailblazer_lt_ext
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Anything over 225ish and I'd be worrying. My s10 blazer gets up there when going in the mountains. But never crazy high and it is worse with the ac pumping away.

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Did this just start happening or has it always been like this when towing?

Mine does the same thing when towing a 5000lb trailer. Either way, I would be interested in knowing if it's normal or not. Sounds like the fan clutch is going.
I would like to know the same thing I'm grossing combined weight 10200 pounds already replace the fan clutch water pump VVT solenoid and transmission cooler and still runs high Temps
 

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I'm trying to figure out this crazy situation. My 04' TB just started overheating when towing our new boat. It doesn't seem to have much of a problem when not towing, but when I tow it can quickly reach 235F once it is on the road for a min.

I turn off the A/C and turn on the cabin heat and the temps move back down to normal quickly. It will also cool down to normal when I stop and let it idle.

I just replaced the thermostat and it seemed like it helped for a few minutes and then the temps started to creep up again until it was near 235F again!

It seems like an airflow problem on the road, but I'm just not sure. It is about to drive me crazy! :duh:

Ram air interference or a clogged core in the radiator.
 

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With all things aluminum, I would try and play it safe and not let it go any higher than the halfway to overheat.

Just for comparison's sake, I have an efan setup in my '00 Jimmy. I was too cheap to buy an actual fan controller so I used a setup basically from a pre-computer '80's Citation that used a temperature switch screwed into the head of the old Iron Duke to actuate the relay for the fan. I used two of those switches, one in a head and the other on the intake manifold. Since these are mechanical switches they aren't that precise and actually found that one actuates before the other, which worked out well for me to not have both fans come on at the same time. The first fan comes on just under the halfway mark (112C/233F) and the other just over, which rarely comes on. So to me, these are "normal" operating temps for the old Iron Duke and 2.8L engines of that era. But they didn't have aluminum components neither.

One last thing. In another thread about a possible failing fan, the possibility exists that the impeller in the pump may have rotted out and may not be pumping right. It may be worth it to pull it to check it out.
Low and slow cruising will point out a defective water pump impeller.
Getting hot at highway speeds is usually a clogged radiator or loss of ram air.
At highway speed, the electric fan is pretty much outta the picture above 30-35 MPH anyway.

BTW: these 'aluminum' engines are designed to run at considerably higher internal temps than the older iron engines. It's an efficiency thing - and besides, GM designed these engines to have a base temp at around 220F or so. Thus, they regulate the temp of the coolant returning to the block, not going to the radiator.

Kinda crazy, huh? It's a new world out there.
 
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