2010 Yukon Denali Overheating when Towing

[j91z28d1]

it depends on the vehicle. some with good air flow it over rides it pretty soon. they have rubber flaps that you can put in the fan shroud they will close with vacuum and open when airflow from mph overcomes the vac from the fan.

 

[Foggy]

This is exactly why I put a manually controlled Efan on my derale trans cooler.
When towing at hwy speeds, the engine fans don't come on but my trans temps
continued to climb. Now I can just flip my toggle switch to bring fresh air thru
the derale trans cooler independent of air incoming to the radiator. It usually drops
my trans temps 10-15* within 1-2 miles. My coolant rarely gets hot due to mu\y
187* thermostat and mishimoto radiator. And removing the factory HD aux cooler
in front of everything has helped my coolant and even my ac perform better without
that extra heat and blockage. I do run a a big ass aluminum pan that holds about
3 extra quarts of fluid too !!

 

[Geotrash]

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.

I have a whole thread on this here, in case it's helpful: https://www.tahoeyukonforum.com/thr...towing-in-the-summer-heat.125753/post-1562470

Long story short though, as others have said, what you're experiencing is pretty close to normal when towing heavy in the summer with a Denali. That said, the radiators in these seem to get less and less effective over time. For best results, I would replace yours with a new one that has the 1.25" thick core. I ran a Cold Case for a while but like they all do, it started leaking, so I installed a Denso OEM-style with the 1.25" core. I also installed new cooling fans for the K5L enhanced cooling package. So far, so good towing 7500 lbs this summer.

 

[Fless]

One thing to check is the condition of the baffles that are on either side of the radiator. They're there to direct cooling air into/through the radiator instead of having it bypass and go directly into the engine compartment. I'm not sure how much they help with electric fans but make sure they're in good condition.

 

[Geotrash]

One thing to check is the condition of the baffles that are on either side of the radiator. They're there to direct cooling air into/through the radiator instead of having it bypass and go directly into the engine compartment. I'm not sure how much they help with electric fans but make sure they're in good condition.

Good call.

Update: it was a hot day today as we pulled our 7500 pound camper over the spine of the Appalachian through West Virginia. No problem keeping the engine and transmission cool with our current set up and replacement radiator. Coolant temperature gauge got up to the three-quarter mark a couple of times, but quickly cooled back down. Transmission maxed out at 217°F.

 

[tagexpcom]

Last Aug, we bought a 2021 Yukon Denali 6.2L but did not have the towing package (e.g. does not have tow cooling). As part of the pre-purchase, we test pulled our 5300lb 7 x 14 dual axle trailer up a 10mile, 6% grade over Mt Ashland with 107F ambient! and it performed A-OK. The trans reached 200F. The engine steady at 210F (normal). Yawn...! Since then, we've towed 5,000+ miles over several 10 mile mountain passes and no issues - e.g. 185F max trans and stead engine 210F with ambient temps <90F.

Don't know about 2010 but I'm guessing it's a very capable rig and that overheating would be due to worn parts or systems and could be restored.