Running Hot!

[Berkyeng]

Hi all

I purchased my 2008 Forest River Berkshire 390BH (Freightliner Chasis, 340hp Cummins 6.7L ISB) about 1 year ago. It has 52,000kms on it (I bought it at 45,000kms). For completeness related to this question, I am flat towing my 2018 Ford Explorer behind it.

Took it on its first trip (with me) over some steeper grades (Salmo, Bombi, and Bonanza Passes in southern B.C.). On the steepest sections of grade (8-ish%) I started building heat in the engine. Needle never made it to “red” and didn’t get any warnings on the dash, and the engine cooled back down within a couple minutes after coming off the grades. The rig and toad slowed to about 50kph (30mph) up these grades in 3rd gear. I do feel like I babied it a bit up these grades as well.

Thoughts on if I have a cooling problem? Outside temps were mid-20s Celsius (70s Fahrenheit) at max, even cooler at the summits.

Any advice greatly appreciated.

Thanks.

[wolfe10]

There is no Tow Haul on Allison 3000 transmission.

And economy mode ON is OK as long as YOU select the proper gear (higher end of engine RPM range and less than full throttle).

If you expect all automatic, then on long steep grades keep it in performance mode (which is the mode it starts in every time you start the engine). The problem I see with that is that you have decided that it is smarter than you. May be true, may not-- depends on the driver.

Said another way, a smart drives is PROactive-- seeing what is happening where you are now and what is coming up. While the transmission can only e REactive-- seeing what happened well behind you.

No rights or wrongs here-- but the Allison does allow you to treat it like a manual transmission in terms of selecting the right gear.

[Cummins12V98]

Transmission use Tow Haul if it has it. Does the engine fan come on???

Simply hold it to the floor going ups steep grades as it will run in the proper gear. NO you will not hurt it!!!

[Berkyeng]

One other thing I forgot to mention was that I drove it in economy “mode” (presses the “mode”button on the tranny control so the red light was on). Is this the right strategy on long climbs or should I be switching out of that when going up hills?

[Berkyeng]

ajriding wrote:
I had a 5.9 with a truck camper and trailer climbing the Rockies and temps stayed level. On big climbs temps would rise, then the thermostat would open, then cool back to high 180's, then close and rise into 190's and cycle back and forth (I had a quality temp gauge so could see this).

I never saw temps go high.

I suspect other issues,
A bad radiator - old and partly clogged- a mechanic shop can look at it with a temp gun and see if there is any clogs.
A bad fan clutch (slower speed climbing might require the fan to run)
A bad thermostat
Is the fan shroud intact and directing air correctly?
Nothing blocking the radiator?

Nothing untoward underneath. Fan shroud completely intact. New coolant last year. Don’t know if the rad is plugged, but like I said the unit only has 52,000kms on it so would struggle to understand why the rad would be in trouble.

I’m going to try and take it to a shop and steam it out. I cannot get under the bed / closet without a cutting torch at this point. Tried pry bars and hammers and the bed compartment is too tight to take apart.

[ajriding]

I had a 5.9 with a truck camper and trailer climbing the Rockies and temps stayed level. On big climbs temps would rise, then the thermostat would open, then cool back to high 180's, then close and rise into 190's and cycle back and forth (I had a quality temp gauge so could see this).

I never saw temps go high.

I suspect other issues,
A bad radiator - old and partly clogged- a mechanic shop can look at it with a temp gun and see if there is any clogs.
A bad fan clutch (slower speed climbing might require the fan to run)
A bad thermostat
Is the fan shroud intact and directing air correctly?
Nothing blocking the radiator?

[wolfe10]

Flan wrote:
What are you considering hot? 210 degrees for short stints is pretty normal usually once cresting the grade they will cool off settle back in around 180-190.

While absolutely true, I would suggest that once coolant temperature rises above thermostatic control (fan on high speed on side radiator systems) one needs to start addressing the condition.

That likely means lower gear, higher engine RPM and backing out of the throttle. Using this technique,we have successfully climbed long 6+% grades in 100 degree weather without coolant temperature rising more than 10-12 degrees F from thermostatic control. And, passed other DP's on the side of the road with severe overheating under exactly the same conditions.

[Flan]

What are you considering hot? 210 degrees for short stints is pretty normal usually once cresting the grade they will cool off settle back in around 180-190.

[Berkyeng]

garym114 wrote:
Don't know where the power RPM range is on your engine but it is probably higher that the RPMs you were doing at 30mph in third gear.

Yes, likely. Was doing about 2100RPM. Thanks for this tip. Will aim for 2700RPM if I have the problem again.

Thanks

[wolfe10]

Berkyeng wrote:
Thanks.

Is there any way to access this from under the coach (knowing full well this will get me wet and dirty!). I’ve been under the bedroom once and the engine cover is so tight it took me 2 days of prying and pounding to get under the bedroom. I really don’t want to go through that again!

Thanks.

You will just have to crawl under and check. Look at the perimeter, not center of the CAC (the fan blades sling the dirt to the perimeter).

And, yes, if overheating, operate about 200 RPM under max HP RPM for your engine at less than full throttle. Higher RPM turns the fan and water pump faster and less than full throttle reduces heat load. Do NOT run dash A/C when overheating.

[garym114]

Don't know where the power RPM range is on your engine but it is probably higher that the RPMs you were doing at 30mph in third gear.

[Berkyeng]

Thanks.

Is there any way to access this from under the coach (knowing full well this will get me wet and dirty!). I’ve been under the bedroom once and the engine cover is so tight it took me 2 days of prying and pounding to get under the bedroom. I really don’t want to go through that again!

Thanks.

[wolfe10]

Clean the front of the CAC as well as radiator. Access from bedroom or closet depending on floorplan.

Needs to be done annually.

A garden hose and Simple Green Extreme (will not harm the aluminum CAC)and an old pair of clothes you don't mind getting dirty is all you need.