Motorhome Overheated on Mt. Pass

[Madrona]

Recently completed a pretty long trip. Part of it was heading west over Sherman Pass out of eastern Washington. It's a fairly steep pass with lots of twists and turns and not much chance to get a run at it. I don't think I ever got out of 3rd gear. Part way up there was a warning for high coolant temperature. The temp guage has certainly been higher than it was when the warning came on. The tranny guage was not much over normal when climbing passes. Ambient temperature was probably in the 80's, maybe a little more. I pulled over (luckily in a shady spot) and shut the engine down. I opened the rear engine cover and everthing looked normal. I left it open to hasten cooling and waited about 20 minutes. Restarted and proceeded up the pass. Just before the summit the warning came on again but I was so close I just proceeded. I don't think it was on for much more than a minute when we crested the summit and started coasting down. The light went out very quickly and the rest of the trip was pretty normal, even though we did have another couple passes ahead of us.

So the question is, does this seem normal? Does hill-climbing in relatively hot temps cause this kind of reaction in a heavy vehicle?

Cummins ISC 330

[Batman_777]

Pull over and for a few minutes, keep the motor running for a faster cooldown. This also gives the turbo time to cool off before shutting the motor off since shutting the motor off with a hot turbo can burn up the turbo.

[RickO]

You bet it does... especially where there are a lot of turns causing you to lose momentum. I learned this the hard way when my coach was new but got a lesson from the Cummins tech. He explained that under those conditions, one really needs to ensure that the RPM is kept (at least on my Cummins ISL400) up near 2000 to 2200 to ensure the fan is moving enough air. It requires a lot of forced down shifts... but you say you didn't get out of 3rd gear so not sure what else you could've done.

If you have a rear radiator, keeping it clean is also important.

Glad you got home ok and good luck on getting a handle on this issue.

Rick

[ga traveler]

Quote:

Originally Posted by RickO You bet it does... especially where there are a lot of turns causing you to lose momentum. I learned this the hard way when my coach was new but got a lesson from the Cummins tech. He explained that under those conditions, one really needs to ensure that the RPM is kept (at least on my Cummins ISL400) up near 2000 to 2200 to ensure the fan is moving enough air. It requires a lot of forced down shifts... but you say you didn't get out of 3rd gear so not sure what else you could've done. If you have a rear radiator, keeping it clean is also important. Glad you got home ok and good luck on getting a handle on this issue. Rick

. Good advice on the RPM's. Remember the water pump is just that, A PUMP. It has to move fast to keep the water going through the radiator and cooling it down.

[Madrona]

Quote:

Originally Posted by Batman_777 Pull over and for a few minutes, keep the motor running for a faster cooldown. This also gives the turbo time to cool off before shutting the motor off since shutting the motor off with a hot turbo can burn up the turbo.

I actually did keep it running just because it seemed like the right thing to do, but after a couple minutes the warning hadn't stopped so I shut it down.

Quote:

Originally Posted by RickO You bet it does... especially where there are a lot of turns causing you to lose momentum. I learned this the hard way when my coach was new but got a lesson from the Cummins tech. He explained that under those conditions, one really needs to ensure that the RPM is kept (at least on my Cummins ISL400) up near 2000 to 2200 to ensure the fan is moving enough air. It requires a lot of forced down shifts... but you say you didn't get out of 3rd gear so not sure what else you could've done. If you have a rear radiator, keeping it clean is also important. Glad you got home ok and good luck on getting a handle on this issue. Rick

Side radiator but I agree, it should stay clean and it is. Sounds like you have confirmed this is pretty normal behavior under the circumstances.

Quote:

Originally Posted by ga traveler . Good advice on the RPM's. Remember the water pump is just that, A PUMP. It has to move fast to keep the water going through the radiator and cooling it down.

Yup, the RPM's were right around 2,000-2,100 in 3rd gear. I guess with the ambient temp the pump just couldn't keep up. Sounds like it's just one of those things to get used to. Luckily, we don't travel in that kind of heat over mountain passes very often.

Thanks to all for advice and confirmation. Again, I feel better now!

[RustyJC]

Is your engine cooling fan drive working properly?

Rusty

[Madrona]

Quote:

Originally Posted by RustyJC Is your engine cooling fan drive working properly? Rusty

Yes, Rusty, that was one of the first things I checked, but good suggestion. I should have mentioned that.

[Francesca]

Sherman Pass is the highest pass in Washington that's open all year!
Some of Hwy 20's steepest, twistiest grades are also on that section.
My experience with Sherman has been that running the vehicle air conditioning while climbing those grades soon overheats the engine...

Francesca

[Bill Adams]

I would suggest that you tried too hard. Speed is not the goal when trying to climb a tall mountain pass and it appears you went for too much speed. Gearing WAY down and taking all the time necessary to make the grade is the proper course. The first time I ran into this I wondered why everyone was going so slow as I was simply cruising up the hill. Then the engine shut down due to overheating and I sat on the side of the road while we cooled down. Once things returned to normal I pulled out, ran in second gear at full RPM and about 25 MPH along with the rest of the truck traffic and climbed to the top without a second thought. I never did that again and I always let the engine tell me how fast or how slow I should climb a hill.

[Madrona]

Quote:

Originally Posted by Francesca Sherman Pass is the highest pass in Washington that's open all year! Some of Hwy 20's steepest, twistiest grades are also on that section. My experience with Sherman has been that running the vehicle air conditioning while climbing those grades soon overheats the engine... Francesca

You're probably right, Francesca, but the AC wasn't on. That's a whole other issue...

[Coma]

FWIW this is the technique I used this summer crossing Vail and Eisenhower this summer, both about 11000ft without over heats. Take the RPM it shifts in normal mode and subtract 50 rpm. Note the max boost produce under these conditions and subtract 4psi. In my ISC that would be 2050rpm and 19 psi as target numbers, as you go up the hill manually select a lower gear as necessary to keep boost at 19 or less while running 2050 RPM. Coolant temps will rise but not over heat. You will see temps in the 200 range.

[frankdamp]

We came up Washington Pass from Winthrop into Western WA yesterday. Our 01 (chassis date) front-engine V-10 handled it just fine. Ambient temp was low 80s and I had the chassis air on mid-speed fan. The water temp gauge never went above the mid-point of the normal segment and the transmission handled the grades and speeds without any input from me. There were a couple of lengthy stretches where we were running at about 35 mph with just over 3000 rpm on the tach.

Very pleased with the performance.

[DtBt]

Monaco side radiator coaches do not usually overheat if working properly unless you try to lug up the mountains, which you obviously did not do. In addition to cleaning the outside of the radiator and flushing the inside make sure the Radiator Thermoswitch is working properly. The fan will operate at a slow rate until the wax valve opens. When the temperature increases the fan should really start to roar. I don't know how to test the switch.

[Land Barge]

I had a similar issue on the trip to Salt Lake when ambient temps were over 105, I have since been informed that under similar loads you are suppose to run peak Hp and not peak Torque, which requires some downshift assistance. I was lugging it because it would pull it on the turbo but now I wind it up higher and don't seem to have any more issues.
Most seem to be in the 2,100 to 2,200 rpm range.