2010 Yukon Denali Overheating when Towing

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Tim907356

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The truck has ~175k miles on it. The background story is that we have been towing a 4200# dry weight Travel Trailer for about 5 years with minimal issues. At first, the transmission overheated, hitting near 230F on one of our first 'mountain' tows on a 90F day, so I put the trucool 40 in line with the oem aux. cooler, which solved the problem.
Well, we just upgraded to a 6300# T.T. a few weeks ago, and drove it home 2 hrs. or so without issue. This past Thursday evening, we towed about 250mi. to our destination arriving at midnight, again without issue. Yesterday on our return trip however, things changed.

First, it was hot out; 95F or so. We got on the same route we came in on with some rolling hills, and 55mph backroads. I noticed the temp gauge picking up from the 210F mark within the first hour of the trip. The transmission kept below 200F, likely due to the trucool, but the engine continued to climb and fall with the load; hills, speed, traffic, etc. Outside temp was 'measured' by the truck at up to 105F, but I think that was influenced by the engine temp., as the weather app. said it was 95F.

I tried to vary the transmission, going from normal drive, to tow mode, to manual shifting to keep it cool. At first, it seemed like higher rpm (3000rpm) would circulate fluid better, but that didn't work longer term. Basically, the only thing that affected the temp was letting off the gas, and slowing to 45mph going up hills. It would sometimes cool back to the 210F point and stay there until the load picked up again. I could hear the fans running too, so it seems that everything was 'functioning' properly. Fluid levels were all topped up; coolant, Transmission oil, and engine oil. No messages or codes were generated that came up, and I was able to keep the engine below 235F the whole time...I had determined this would be my pull-over and cool off temperature

I'm game to do the conventional coolant purge, thermostat change, oil & tranny fluid change if that's all that's needed. But these are all done on a conservative maintenance schedule. And the truck runs/cools normally at all other times, and with more modest loads, never leaving the 210F mark.

Anybody have any upgrade recommendations? The addition of the trucool was a great change, so in the same vein, I'm thinking a larger, secondary or more efficient radiator recommendation, better or additional fans.

Edit; electric fans only; no clutch/fan on this one.
 
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Big Mama

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It could just be that it was really hot and you’re towing if all systems work properly ie no boiling coolant or over flow spilling over. There are some coolants out there that claim they run cooler but I can’t speak to that. Have you weighed your set to see where you are fully loaded?
 

strutaeng

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How fast were you going? I guess you need to stay with traffic which is reasonable.

Does your vehicle have an engine oil cooler? If not, can one be added?
 

Marky Dissod

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There's some sort of electrical test for the radiator fans.
If they draw too much current, they are aging out and will need to be replaced soon.

GM OE program turn the fans on LOW @ 226F, and turns them on HIGH @ 235F.
My pcm tune turns them on LOW @ 217F, and turns them on HIGH @ 226F.

Also, my Tow / Haul shift table is customized to better protect the transmission.

What axle gear does your Denali have? 3.08? 3.42 would be better for the powertrain.
 
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Tim907356

Tim907356

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There's some sort of electrical test for the radiator fans.
If they draw too much current, they are aging out and will need to be replaced soon.

GM OE program turn the fans on LOW @ 226F, and turns them on HIGH @ 235F.
My pcm tune turns them on LOW @ 217F, and turns them on HIGH @ 226F.

Also, my Tow / Haul shift table is customized to better protect the transmission.

What axle gear does your Denali have? 3.08? 3.42 would be better for the powertrain.
I have no idea on the ratio....Stock? I'm sure it wasn't used for towing before we got it in 2020 (used).
 
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Tim907356

Tim907356

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I talked to a friend, who said 'don't worry about it'...that 235 is safe to run. Even if so, the thermostat has always been my mental governor for appropriate engine temps, and I'm inclined to get it back to 210-212 if at all possible.
 
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Tim907356

Tim907356

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How fast were you going? I guess you need to stay with traffic which is reasonable.

Does your vehicle have an engine oil cooler? If not, can one be added?
55mph on the backroads. I tried wicking it up once we hit the interstate, but that's where the temp hit 235, and I backed off to 50-55 again.
It doesn't have an oil cooler that I can find/see, but that would be a good idea...is there an aftermarket kit to add one?
 

strutaeng

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55mph on the backroads. I tried wicking it up once we hit the interstate, but that's where the temp hit 235, and I backed off to 50-55 again.
It doesn't have an oil cooler that I can find/see, but that would be a good idea...is there an aftermarket kit to add one?
I see. If the temperature stabilized at 235F, that may be okay.

You can use factory parts to add the engine oil cooler, which is simply the cooler lines and the radiator that had the engine oil cooler option. It goes on driver's side on top of the oil filter. Just remove the block off plate and install the new lines. You will have to replace the radiator.

The engine oil cooler option was standard on all 2500 SUVs (as well as 2500 HD+ trucks) as far as I know. It was more like for a towing setup. I'm not sure if 1500s got them, maybe only a few of them if they had that RPO code? I've never owned a 1500 SUV, so IDK.
 

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