Towing and temperature issues

[lectric74]

I have an 12 Yukon XL 5.3 with all the heavy duty trailer options (JL1, K5L, KNP, Z82, 8k rating), and I tow a 24' camp trailer that weighs in at about 4500, give or take, with a WD hitch. Towing down to my house this last weekend I noticed that with the A/C running (94 outside), that my engine temp would climb to the 3/4 mark, and trans temp was about 220 at the highest, averaging around 210. I could turn the A/C off for a bit, get hot in the truck, then turn it back on and the coolant temp would drop for a while to 210, with trans about the same, but would creep up slowly.

Question is, before I tow a bit longer this weekend, is there anything I can do to help keep that temp lower that isn't going to cost a lot? It already has a heavy duty trans cooler, radiator, oil cooler, and the 2 speed cooling fans, but is there anything I can do to help that temp stay a bit lower. The trip this weekend has a few fairly steep hills to climb, and I'm leaving earlier in the day so it will be cooler, but anything else that might help? Any additives to the cooling system that might help keep that temp a bit lower? Anything I need to check? Outside of towing the Yukon has been absolutely flawless, even with 219k on the clock, so I'm hoping this isn't a serious issue, but want to ask.

 

[swathdiver]

I have an 12 Yukon XL 5.3 with all the heavy duty trailer options (JL1, K5L, KNP, Z82, 8k rating), and I tow a 24' camp trailer that weighs in at about 4500, give or take, with a WD hitch. Towing down to my house this last weekend I noticed that with the A/C running (94 outside), that my engine temp would climb to the 3/4 mark, and trans temp was about 220 at the highest, averaging around 210. I could turn the A/C off for a bit, get hot in the truck, then turn it back on and the coolant temp would drop for a while to 210, with trans about the same, but would creep up slowly.

Question is, before I tow a bit longer this weekend, is there anything I can do to help keep that temp lower that isn't going to cost a lot? It already has a heavy duty trans cooler, radiator, oil cooler, and the 2 speed cooling fans, but is there anything I can do to help that temp stay a bit lower. The trip this weekend has a few fairly steep hills to climb, and I'm leaving earlier in the day so it will be cooler, but anything else that might help? Any additives to the cooling system that might help keep that temp a bit lower? Anything I need to check? Outside of towing the Yukon has been absolutely flawless, even with 219k on the clock, so I'm hoping this isn't a serious issue, but want to ask.

Hi Jason, are you asking about the transmission or coolant temps or both? As for the engine cooling system, make sure the fluid is less than 5 years old and still the right mixture. The transmission fluid has a service life too that is visible with a scan tool as a percentage but if you've recently changed it, those temps are fine.

GM doesn't consider the transmission temp hot until it gets up into the 260s.

The ECT gauge on the dash is purposely designed not to move around much and at normal cruise, the temperature is actually lower than it shows, around 195. If the temps begin to climb past 210, it will then show a more accurate reading. This was done so as not to alarm the driver (such as soccer moms) as the temperature moved throughout its designed operating range.

If you head into the hills, stick her in 4th gear, that's what the shop manual says is the preferred gear for towing, this spins the motor to cool the engine proper while towing and 4K rpms is nothing to these LS motors. My guess is that you were towing in 5th or 6th when the coolant got that hot?

 

[lectric74]

I was in Tow/Haul mode with the trans typically staying in 5th, but I will switch over to manual, especially on the hills, and kick it down to 4th. I was more concerned with trans temps, as that's quite a bit higher than I see under typical conditions, but glad to hear it isn't as bad as I thought.

Water temp did stay in the "normal" range, I will have to watch with Torque to see what the actual temp is when I'm towing. It's just a bit nerve wracking to see it at the 3/4 mark (255 is what that would typically mean on the gauge), and I wasn't sure if this was something to be concerned with.

No idea on coolant age, as I only bought this last month, but I'll add a coolant flush to the list of things to do. It likely won't be before this weekend, so I may try something like Water Wetter to try to keep it a bit cooler, without having to do a full flush that I don't have time to do. I still have front/rear diff fluids to do, trans flush, transfer case drain/fill, and a few other minor things like replacing the screen and oil pressure sensor, as it reads low and triggered the SES.

Thank you swathdiver!

 

[swathdiver]

I was in Tow/Haul mode with the trans typically staying in 5th, but I will switch over to manual, especially on the hills, and kick it down to 4th. I was more concerned with trans temps, as that's quite a bit higher than I see under typical conditions, but glad to hear it isn't as bad as I thought.

Water temp did stay in the "normal" range, I will have to watch with Torque to see what the actual temp is when I'm towing. It's just a bit nerve wracking to see it at the 3/4 mark (255 is what that would typically mean on the gauge), and I wasn't sure if this was something to be concerned with.

No idea on coolant age, as I only bought this last month, but I'll add a coolant flush to the list of things to do. It likely won't be before this weekend, so I may try something like Water Wetter to try to keep it a bit cooler, without having to do a full flush that I don't have time to do. I still have front/rear diff fluids to do, trans flush, transfer case drain/fill, and a few other minor things like replacing the screen and oil pressure sensor, as it reads low and triggered the SES.

Thank you swathdiver!

My pleasure sir! She'll run a whole lot nicer with fresh fluids in the drive train. Good luck and let us know how she tows and grab a pic or two of the whole set up if you can.

 

[lectric74]

I can say towing it home was about 92 miles, and she towed like it wasn't there. Trailer braking was solid once I got the gain adjusted to my liking, and it was easily able to hold 65-70 even with a bit of a headwind. My Dakota with a 6 spd. manual and 4.7 was a chore to even maintain 60, typically in third if there was a head wind, fourth if not, but never into 5th or 6th unless it was downhill, then it wouldn't be shifted up anyway, and always getting passed on hills by semi trucks. I'll try to get some pictures, where I store the trailer at home I can't get a shot, but I should be able to get one at the campground we are staying in.

 

[97audia4]

I have had the temp go up to about 225/ 230 but it has always gone back down while towing and never above that . It seemed to cycle while in tow haul mode . This was 5000 lbs extra height enclosed trailer

 

[lectric74]

I will watch it using my OBDII reader and Torque this weekend when I'm towing. This trip is 180 miles each way, and has a few fairly steep grades to climb, but I think I'll be ok. I do have a new oil pressure sending unit and the filter that I'm going to replace tomorrow, that should resolve the low oil pressure readings that have been popping up lately and tripped the SES. The Yukon has 219k miles, so I'm sure that filter is the real issue, but I'm not about to replace the screen without doing the sending unit.

I'll have to do a bit of research on logging things, so I can log the entire trip and see what the temps are really running. ECT appears to be staying in the normal range, but I'm still adding a bit of Water Wetter to help keep it a bit cooler until I can get a full flush done.

 

[97audia4]

There is also a pressure relief valve on the expansion tank. I had mine go bad, didnt notice it until it actually started to leak coolant ever so slowly that could be lowering the psi of the cooling system pressure and making it less effective.

 

[lectric74]

There is also a pressure relief valve on the expansion tank. I had mine go bad, didnt notice it until it actually started to leak coolant ever so slowly that could be lowering the psi of the cooling system pressure and making it less effective.

Where is this valve located? I'd like to check it out.

Trip went well, overall engine temps peaked at 240, according to Torque, with trans peaking at 220. Outside of that, which I don't like 240 on a gas engine, everything worked exactly as expected. I did not add any additives, I'm going to focus on getting a flush done in the next week or so, after I get the trailer hauled back to my property for the rest of the summer. No pics, things were hectic and I forgot, but I will get pics when I haul the trailer up this weekend.

 

[97audia4]

Where is this valve located? I'd like to check it out.

Trip went well, overall engine temps peaked at 240, according to Torque, with trans peaking at 220. Outside of that, which I don't like 240 on a gas engine, everything worked exactly as expected. I did not add any additives, I'm going to focus on getting a flush done in the next week or so, after I get the trailer hauled back to my property for the rest of the summer. No pics, things were hectic and I forgot, but I will get pics when I haul the trailer up this weekend.

On the bottle of the tank near the bracket for the air box. Its a small hole, I would go for a drive and get the car hot and look under the bottle where the fender liner is you will see drips. I never noticed it until I shook the bottle and saw it start to drip.