Cummins diesel water temp when climbing?

mjurgen889 · 07-21-2012, 07:57 AM

Just climbed through the Eisenhower Tunnel west of Denver. I have a 40' Itasca Horizon with the 400 hp Cummins turbo diesel. During the initial climb out of Denver on a very hot day, I got as high as 235 deg. - very hot in my opinion. I slowed and crawled a bit and got the temp lowered to around 220 or so. Never got much higher than that.

Having never owned a diesel, I honestly had no idea when to pull over and cool although I would definitely done that if it had gotten any higher. My temp gauge doesn't have a red zone and I haven't read much about when hot is "too hot".

Also, what's the best strategy for high mountain crossing - slow go all the way or make a run at a moderate speed, then slow to maintain a lower temperature? We go back in two days and start with a steep climb early in the am to the Eisenhower tunnel.

As always, thanks folks for all your help! This forum is a life saver for new folks!

Mike

Steve Ownby · 07-21-2012, 08:36 AM

Mike,

The strategy for long climbs is rpms as high as possible. This is where you are smarter than the Allison. The computer managing your transmission cant know what kind of demand is coming up. When you start the climb and the rpms start falling at WOT, you should manually downshift a gear to get the rpms up close to governed engine speed. If the rpms start falling again, downshift again. The idea is to keep engine speed up so it's operating close to the peak hp which is up close to governed speed. This high rpm keeps the coolant moving at top speed. If rpms stabilize and the temp still climbs, downshift another gear and back out of the throttle some.

Triker56 · 07-21-2012, 08:47 AM

Never let the transmission hunt between 2 gears. Use Manual to downshift.

Wayne M · 07-21-2012, 10:16 AM

Mike,
I have the Winni with the 340 Cumins. Steve gives good advice. In my particular case, and from what I gather from other is a pretty good standard, 2000 RPM will keep the temp down. I have my temp on the LBCU display and when it starts climbing up past 207-208, I start the downshift process and maintain 2000 rpm. It drops me back down to 204-205 real quick. Just find that sweet spot, maybe starting at 2000 RPM and see what happens. Adjust accordingly. Others with the 400 may have a more accurate RPM for that engine.

mjurgen889 · 07-21-2012, 04:09 PM

Gee - feel a little dumb now. Several times I thought it made sense to downshift to increase flow, just had never read about it so I left it alone. We climbed at 1500 RPM (6th gear/automatic mode) so that was the problem. Now I know better. Thanks guys!

On the way down, I did downshift and used the low engine break setting. Had read about that as a strategy and it worked perfectly going into Silverthorne.

OK, relieved! Do any of you also turn off the engine driven AC to eliminate an additional load on the engine?

Thanks a lot guys - always good advice for me here!

cardiffman · 07-21-2012, 04:44 PM

Steve gives great advice. "keep them R's up!" Try to anticipate the need for more power and avoid lugging the engine. I found in my former coach with a 350 Cummins/Allison combination that, if I waited for the transmission to kick down, it was too late. From my old truck driving days, you drive by the tachometer and the engine temperature gauge. You can keep the temps down by continuing to down shift to keep R's up. On the Baker Grade from LA to Vegas at 110 ambient temperature and 50,000 lbs of cargo, the trucks crawl along but seldom overheat. Modern Electronic engines have "idiot driver proof" computers that will slow down the flow of fuel if the temperatures get too high or RPMs get too high. Happy Camping!

Ramzfan · 07-26-2012, 10:10 PM

I had a 2000 Discovery with a 5.9 Cummins in it. I had a serious overheating problem coming through New Mexico last year. I tried keeping the revs up, slowing down to a crawl, even stopping and letting it cool down every few miles. When I got home, I took it to Cummins and found out that the radiator was caked with dirt and oil from the "slobber tube."
They power-washed it, drained and refilled the radiator and I never had another overheating problem.

Texas TC · 07-27-2012, 07:23 AM

And, make sure your coolant is in filled to the higher range in the reservoir. I actually had the hot display the first time I climbed I40 west out of Albuquerque. Camp Freightliner a couple of weeks later taught me to keep the coolant filled to the higher end of the range and I have never had a heating issue again. And, I let the Allison do it's thing and have never used the manual shift mode on the pad. I climbed I70 last week going east toward Frisco/Breckenridge from Montrose. Even climbing to 10,600 feet, speed reduced to 50 mph, towing my Silverado, I never had a heat issue. Just another train of thought initiated by Mike Cody at Camp Freightliner.

mjurgen889 · 07-30-2012, 05:04 AM

I followed Steve's recommendations and the others that were so kindly posted. No problems at all - worked like a champ with temp never exceeding 203 deg. on the climb out. Thanks to all for the help.

We decided to downsize on return and traded to an Itasca Meridian V 34Y. It's just right for us and lightly used - literally just broken in. Still a pusher with the features we wanted.

Mike

Largeandy · 07-31-2012, 04:22 AM

Quote:

Originally Posted by cardiffman

Steve gives great advice. "keep them R's up!" Try to anticipate the need for more power and avoid lugging the engine. I found in my former coach with a 350 Cummins/Allison combination that, if I waited for the transmission to kick down, it was too late. From my old truck driving days, you drive by the tachometer and the engine temperature gauge. You can keep the temps down by continuing to down shift to keep R's up. On the Baker Grade from LA to Vegas at 110 ambient temperature and 50,000 lbs of cargo, the trucks crawl along but seldom overheat. Modern Electronic engines have "idiot driver proof" computers that will slow down the flow of fuel if the temperatures get too high or RPMs get too high. Happy Camping!

Have a brand new 2012 Itasca Ellipse, 450 hp cummins and of course a tag axel. Recently Bought the Ellipse in Mesa, AZ then Drove from Fountain Hills, AZ up the Beeline Highway to Payson, Az. The Cummins quickly hit he red temp zone when going up the steep grades while pulling our grand Cherokee. Check engine light came right on, showed coolant was low so I stopped and bought more coolant and then luckily was out of the steep grades and then stopped to let engine and radiator cool so coolant could be safely added.

Bad situation as I was trapped going up a small highway in thick traffic with NO PLACE TO PULL OVER, did best I could to manage the RPM's and keep the temp needle below the RED ZONE, which worked if I slowed to an absolute CRAWL!

DEALER and SERVICE DEPT. were supposed to have checked this but AS USUAL, this did not happen as I was told. I guess no surprise in the RV world!

On way home to New Mexico, rig did better but I have been disappointed in the engine pulling performance of this new rig. I am sure I have a lot to learn on how to "manage" the uphill engine temps with rpm's and coolant levels but honestly, my two previous 40' DP's NEVER FOUGHT THIS PROBLEM! I had high hopes for the 450 HP Cummins in this gorgeous 43 ' tag axel but I am not so sure the engine is enough of a match for the aded weight that comes from the 3 more feet of length and the extra 10K pounds added thereby.

I had a 2003 Alpine and a 2011 Phaeton 40' non tag axel DP's with 400 hp and 380 hp Cummins engines that did far better up hills while pulling similar weighted toads. Never once had any "red zone" high temps in either one of those. The Allison in both cases handled the rpm problem just fine......never had to think about it as the temps NEVER GOT UP LIKE THEY DO IN THIS ELLIPSE. I definitely love the roominess and creature comforts of this new Ellipse but it has issues when it comes to driving that neither of my previous rigs had. I would not have expected that this issue would be yet one more issue to put on the list!

Lault · 07-31-2012, 07:14 AM

Largeandy, also have the same drive line in my 12 Revolution and will be going up I 70 and the tunnel in 12 days. I will see what happens. I also had a 11 Phaeton 40 QBH with no issues climbing mountains. The Rev. had no issues coming from Santa Fe. I sure hope for better results than you had.

Steve Ownby · 07-31-2012, 07:30 AM

I hear your disappointment in your new coach. The Ellipse is truly a beautiful motor home. I'm sure your problem has a solution. I consider Winnebago to be thorough engineers and chances are good that this is a malfunction not an engineering flaw.

I assume, when pulling a grade the Allison downshifts at around 2100 rpm. What was your rpm range when the over heating started? How much coolant did you have to add to get the level up? Are you getting your temp from the analog dash gauge or do you have an electronic engine monitor which gives you that.

Once you added the coolant, how did the temp do. Cruising on flat land what is the temp? Is it possible that the dash light was triggered by the low coolant sensor and the dash gauge is not giving you a correct temp. I believe you have a side radiator. When you stopped to let the engine cool did you walk to the back of the coach? Could you hear the fan? It should have been making a lot more noise than when cold. It's possible the fan controller is malfunctioning & not running the fan on high.

Do you have a boost gauge on the dash? If you have a leak in the CAC plumbing it could cause a loss of power and contribute to the overheating.

Bottom line, after all my incoherent rambling, Winnebago/Freightliner can solve your problem. If nothing simple shows up, get them to make an appointment with a Freightliner dealer with a Dyno and they should be able to solve your problem. If you have plans to travel to the east, Gaffney, SC is where they build the chassis and they have very knowledgable techs.

Let us know ow it turns out.

chief02 · 07-31-2012, 07:37 AM

Just be carefull of high exhaust gas temps when pulling at high RPM's. Severe piston damage will result.

RickO · 07-31-2012, 07:46 AM

Quote:

Originally Posted by mjurgen889

I followed Steve's recommendations and the others that were so kindly posted. No problems at all - worked like a champ with temp never exceeding 203 deg. on the climb out. Thanks to all for the help.

When climbing in hot weather I try to:

1) makes sure my radiator has been externally flushed clean

2) hit the grade with a reasonable head of steam because once momentum is lost climbing a hill it's gone forever.

3) manually downshift when temps begin to climb >200 to keep RPM around 2000.

Best of luck

Rick

YC1 · 07-31-2012, 08:02 AM

With my 08 400 ISL I hit the hill with as much momentum as possible and floor the pedal. I let the computer do the shifting as much as possible but if it tries to hunt I will manually drop a gear and back off the throttle a tad to keep the rpms just below redline. The computer won't let you over rev. As for turning the AC off I tried this a couple of weeks ago on a long drive up Donnor Pass in California. I did not notice any difference at all which surprised me a bit. My temps went to about 225. As soon as I cressed the top the temps dropped like a rock. I do keep my radiator very clean. Every time I wash the MH the radiator gets a good basic cleaning. Note during that climb I was towing 4K lb toad on a hot day. It was about 90 at 5000 feet so the engine was doing a fine job.

Ramzfan · 07-31-2012, 08:12 AM

Largeantry, my first question is: Why was your coolant low? Do you possibly have a cracked coolant reservoir? Is your radiator cap good? Any leaks in the system? When you said that you had to add coolant, that tells me that could be the reason for overheating.

Largeandy · 07-31-2012, 11:41 PM

Good questions all, I never thought I would have to work so hard to find answers but I will attempt to do my best.

Thanks to all of your god questions, I hope they lead me in a good direction.

I hope I find some simple answers.

Thanks to all who contributed to my debacle.

Largeandy

Mr_D · 08-01-2012, 12:09 AM

Quote:

Originally Posted by YC1

With my 08 400 ISL I hit the hill with as much momentum as possible and floor the pedal. I let the computer do the shifting as much as possible but if it tries to hunt I will manually drop a gear and back off the throttle a tad to keep the rpms just below redline. The computer won't let you over rev. As for turning the AC off I tried this a couple of weeks ago on a long drive up Donnor Pass in California. I did not notice any difference at all which surprised me a bit. My temps went to about 225. As soon as I crested the top the temps dropped like a rock. I do keep my radiator very clean. Every time I wash the MH the radiator gets a good basic cleaning. Note during that climb I was towing 4K lb toad on a hot day. It was about 90 at 5000 feet so the engine was doing a fine job.

On our Dutch Star the condenser for the air con is totally separate from the engine cooling package. Turning it off or on really doesn't directly affect the engine/trans temps. although it does take some HP away. Sounds like yours is the same.

Largeandy · 08-13-2012, 04:48 AM

Quote:

Originally Posted by Steve Ownby

I hear your disappointment in your new coach. The Ellipse is truly a beautiful motor home. I'm sure your problem has a solution. I consider Winnebago to be thorough engineers and chances are good that this is a malfunction not an engineering flaw.

I assume, when pulling a grade the Allison downshifts at around 2100 rpm. What was your rpm range when the over heating started? How much coolant did you have to add to get the level up? Are you getting your temp from the analog dash gauge or do you have an electronic engine monitor which gives you that.

Once you added the coolant, how did the temp do. Cruising on flat land what is the temp? Is it possible that the dash light was triggered by the low coolant sensor and the dash gauge is not giving you a correct temp. I believe you have a side radiator. When you stopped to let the engine cool did you walk to the back of the coach? Could you hear the fan? It should have been making a lot more noise than when cold. It's possible the fan controller is malfunctioning & not running the fan on high.

Do you have a boost gauge on the dash? If you have a leak in the CAC plumbing it could cause a loss of power and contribute to the overheating.

Bottom line, after all my incoherent rambling, Winnebago/Freightliner can solve your problem. If nothing simple shows up, get them to make an appointment with a Freightliner dealer with a Dyno and they should be able to solve your problem. If you have plans to travel to the east, Gaffney, SC is where they build the chassis and they have very knowledgable techs.

Let us know ow it turns out.

Steve

As a follow up I took the coach out on a shorter 300 mile round trip to have service done on my King Dome this past weekend. On the way home I pulled our Grand Cherokee up some steeper grades. Keeping the rpms up around 2200 to 2350 kept the temp gauge no higher than the third quartile on the a Ellipse temp gauge. I do not have a temp gauge that show true temps, only 4 quartile marks and of course, the RED zone is at the end of the fourth quartile.

The advice to manually downshift to the higher rpm's at around 2200 plus minus WAS EXTREMELY HELPFUL, so thank you and others who pointed that out.

I do have an appointment with a FREIGHTLINER and CUMMINS dealer to get my chassis shimmy at 60 mph looked at. While there I am going to have the rig put on the dyno to see if there are other problems.

Once I get these two ends of the balloon down, I will be in a better mind set but I sure have had my assignment in dealing with so many issues on a brand new rig.

Once again, thank you for your advice and help, it has made a difference.

Andy

skidworth · 08-14-2012, 10:36 AM

I live in Colorado and cross mountain passes almost every weekend in the winter and summer going racing or sledding with a very under powered coach 230 hp pusher and I pull a heavy load 27' enclosed trailer with sleds and gas etc..

Every motor has optimal "torque curve" this has almost nothing to do with HP if you have a 600 hp monster and try to pull Wolf Creek Pass at 1500 rmp it will heat. Research the torque curve area of your motor (simple Google search) mine is between 1950 and 2200 this is where I pull all hills and sometimes in extreme heat the entire trip to keep the temps down and trust me this is where the engine is happy and believe it or not the most efficient on fuel. The biggest issue here is exhaust temp like stated above and not engine temp as much, is 230 hot yes but if you are lugging the motor at 1600 RMP and running 230 coolant temps if you had a exhaust temp gauge it would scare you. On a longer pulls at this constantly if you had a camera in the engine compartment, the exhaust manifold would more than likely be glowing. This is a common issue with used coaches a blued exhaust manifold, missing bolts, etc... very scary if that exhaust got that hot, how hot were the valves letting the exhaust escape? My biggest issue with heating is that I don't have a side mounted radiator and when pulling a trailer in 110 degrees air temp and 140+ asphalt temp the motor is pulling air from under the coach so is passes by a hot motor, transmission and off the pavement.