2008 6.6 running hot towing in the Mountains

[Nilator]

Hi,
I am new to this forum. I have a 2008 6.6 3500HD Dually. Towing a 7,000 lb Fifth Wheel. I notice the other day while going up a pretty good grade here outside of Denver. That the temp was almost up to 3/4 on the gauge. It was not hot out and all fluids are good. Also I was not speeding. Doing about 55. I have done the same drive twice before and did not notice that happening. Do these engines run hot while towing loads up grades? Once the road flatten. Ii cooled down quick. Thanks. Nile

[More Power]

What was the vehicle speed and engine rpm?

Jim

[rapidoxidationman]

Could you hear if your cooling fan was engaged or not?

[Mark Rinker]

The latest body style increased air flow through the cooling stack significantly by increasing the grille area substantially. Result is a cooling fan that rarely needs to engage during 'normal' towing conditions.

Similarly, my 2009 K3500 sometimes takes awhile to kick in - often allowing the gauge to read as high as 240 or so before engaging the fan, and quickly pulling things back into range.

In the past, it seems as if the fan came in sooner, but that costs power and fuel mileage. I think its definately recalibrated with the LMM - very different than the behavior of the LBZ or LLY...

My thought? Relax and drive. Sounds like you are doing the most important thing, which is slowing down in the heat and/or in the hills.

[Nilator]

I could not tell if the cooling fan was working or not.

I would say my speed was 50 to 55. RPM had to be around 2000. The engine was not struggling at all.

I was hoping others in this forum had 6.6 Duramax diesel's an towed up grades.

Thanks for the replies. Nile

[Mark Rinker]

Your last post helps.

When I see the temp rising under these conditions, I'll pull the gear selector into manual shift mode, using the paddle shift control to downshift a gear (or two). Getting the RPMs up will increase coolant flow and fan speed, keeping the temps in check.

[Nilator]

Mark,
You posted your reply as I was typing my new one. That helps a lot. I was thinking of taking in to the dealership to look at, but I guess I will not worry about it right now. I am getting ready to purchase a Fifth Wheel that the GVW is 14,000. This is why I started asking opinion's.
Thanks again. Nile

[Nilator]

Mark,
Now I see. I leave in 2 weeks for another trip up the same grade. I will do like you said and manually shift to a higher gear. I will post a reply on how it went.
Thanks again.

[JohnC]

I could not tell if the cooling fan was working or not.


Then, unless you are deaf, it wasn't working. When the fan clutch engages there is a noticeable drag on the engine and a noticeable roar above 1800 RPM or so. Sometimes you can hear this sound on a cold start, for the first mile or so, then it goes away.

[Nilator]

Well I finally got to test my GMC after everybody replied. Yes, that was the issue. Since the Fifth Wheel is so light (7,000). The RPM's were low even on steep grades. Once I put it in Manual drive and kicked it down a gear. The clutch fan kicked in and cooled the engine down to 210 while I was still going up the grade. Thanks. Nile

[Cougar]

I was towing a 12M lb 5th wheel across Sam's Gap going East on I-26 at the TN-NC state line when my temp went past 210 for the first time. I stopped at the summit for only a couple of minutes and the temperature went back to 210. I was in tow mode and I think the transmission had down shifted one gear. I have no idea if the fan came on or not. I was concentrating on watching the temperature gauge. Thanks for the info on the toggle switch.

[Mark Rinker]

Past 210? Not unusual. Had the fan clutch engaged yet?

I have run 220 for hours...

[Cougar]

210 is my normal cruising temperature and this was the only time the gauge had gone higher. I have done numerous pulls up and down the Cumberland Plateau on I-40 between Knoxville and Nashville with no temperature issues.

I hear an extra noise from the engine compartment, but I do not know if it is the fan or the turbo charger. I am a new diesel owner with much to learn.

[Mark Rinker]

Not much turbo noise on these trucks. If anything, a slight whine on loaded acceleration is all.

The WHOOOOOSH or 'ROAR' that you hear from underhood during high water temperature events is the fan clutch engaging.

Welcome aboard...READ READ READ all the answers are in the forums...