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Old 05-17-2006, 12:38 PM   #1
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I made this post on rv.net, but thought I'd also cross post it here. I'd appreciate any insight the group has.
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We have put about 10,000 miles on our coach in all kinds of terrain and I have never seen the engine temperature climb off the 200 degree mark.

The situation:
Cummins ISL, side radiator, Freightliner chassis. As far as I know, there have never been any recalls by Freightliner on my specific chassis for anything. (This chassis as built up by Thor in their Mandlay did have a recall for fan/cooling issues and some Allegro Buses had some cooling problems several months ago)

Today in the Black Hills our engine temp got up to 222 degrees while climbing a long and fairly steep grade on Hwy 16 out of Rapid City on our way to Keystone, SD.

The ambient air temperature was about 80 degrees, our coach was almost at gross weight (31,400 with 32,000 max) and we were pulling a Jeep that weighed 4,840. Coincidentally we just weighed the coach since I'm trying to offload the front axle a little.

I had the Allison mode selector in the 'economy' position like I always do. We started up the hill at a fairly low speed - perhaps about 45 or 50 mph. Our RPMs were staying in the 1500s range during the hill climb until I intervened.

Once I noticed the temperature at alarm stage I downshifted the transmission to 4th gear to get the RPMs up to 2,000. The temperature did respond by coming down to a little over 200. Every grade after that I had to downshift to 4th gear to manage the temperature. Finally I took the mode switch off the economy setting so we would kick down into a lower gear quicker and have the RPMs come up much more than the 'economy' mode.

Do I have a fan problem, some other kind of problem, or is this normal performance??
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Old 05-17-2006, 12:38 PM   #2
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I made this post on rv.net, but thought I'd also cross post it here. I'd appreciate any insight the group has.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We have put about 10,000 miles on our coach in all kinds of terrain and I have never seen the engine temperature climb off the 200 degree mark.

The situation:
Cummins ISL, side radiator, Freightliner chassis. As far as I know, there have never been any recalls by Freightliner on my specific chassis for anything. (This chassis as built up by Thor in their Mandlay did have a recall for fan/cooling issues and some Allegro Buses had some cooling problems several months ago)

Today in the Black Hills our engine temp got up to 222 degrees while climbing a long and fairly steep grade on Hwy 16 out of Rapid City on our way to Keystone, SD.

The ambient air temperature was about 80 degrees, our coach was almost at gross weight (31,400 with 32,000 max) and we were pulling a Jeep that weighed 4,840. Coincidentally we just weighed the coach since I'm trying to offload the front axle a little.

I had the Allison mode selector in the 'economy' position like I always do. We started up the hill at a fairly low speed - perhaps about 45 or 50 mph. Our RPMs were staying in the 1500s range during the hill climb until I intervened.

Once I noticed the temperature at alarm stage I downshifted the transmission to 4th gear to get the RPMs up to 2,000. The temperature did respond by coming down to a little over 200. Every grade after that I had to downshift to 4th gear to manage the temperature. Finally I took the mode switch off the economy setting so we would kick down into a lower gear quicker and have the RPMs come up much more than the 'economy' mode.

Do I have a fan problem, some other kind of problem, or is this normal performance??
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Old 05-17-2006, 01:40 PM   #3
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John,

I believe this is normal. I have had same experience with my 400 ISL. Today, while traveling on I-80 in Nevada we were climbing a long hill with the ambient temp around 80 degrees. I noticed the engine temp start to climb so I manually downshifted to 5 and then to 4 taking the rpm to approaching 2000. It cooled back to normal and I continued the climb. Upon reaching the summit I shifted back to 6.

The first time this happened to me with similar conditions in Utah it caught me by surprise. Now, I keep an eye on temp guage whenever we start climbing the larger mountains.
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Old 05-17-2006, 02:32 PM   #4
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John,

This was discussed over on RV.net a month or 2 ago. LK23 has to do the same thing I do with my CAT C7- 350 at 30,000 lbs pulling the Mini at 2500 lbs. I watch the tranny and engine temp closely on a long climb. When the engine gets up to around 200, I down shift manually and get the RPM's up around 2000 to 2100. This cools things down.

I cannot speak for your engine but that is how I manage the engine temp on long climbs.

I do not leave the Econo mode set on the tranny so it is easier to do the manual shifts.
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Old 05-17-2006, 02:42 PM   #5
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I had a similar experience this weekend comming out of Needles, Ca. 95 degress , A long 10 mile grade fully loaded and by the time I got to the peak it was at 218 but came down right away, I could have lowered it by reving up in lower gear but I heard that 220 or less for short periods is ok. When I first got the coach it overheated real bad in any heat so I took it to a freightliner dealer and they adjusted the hertz on the fan clutch or whatever and now only on extreme grades with high external temps does it go up high. When I did overheat it before it blew a lot of the fluid out so make sure to check the level witch is not easy to do with the plastic resevor they built the coach with.
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Old 05-17-2006, 03:33 PM   #6
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when i was asking questions after we bought our journey, one ? i asked was about hill climbing,book says 1500rpms max torque is best but forum members said raise rpms 2000-2100 if temp starts to rise
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Old 05-17-2006, 04:20 PM   #7
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John my 400isl in a vestra pulling a suburban (5300) last summer in arizona long grade outside temp was in 90s, hot engine alarm and engine defueled. dropped trany to 4th gear and
the engine cooled down. Note I ras running cab
air, was later told under described conditions, run house air, and not cab air, tip from long haul truck driver, ok since then
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Old 05-17-2006, 04:53 PM   #8
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Thanks everybody for the responses. It appears that things are nominal for the situation.

What I think I ought to do is to spray some Simple Green on the radiator and rinse it off with water. We drove through quite a bit of dust today and a week ago coming and going to the last campground.

If the air temp is really warm, I'll bite the bullet and run the genny for the house AC instead of the dash air.

We'll see how it goes in a few days when we leave this area.
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Old 05-17-2006, 05:44 PM   #9
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I always spin my ISL in the 1900 to 2100 rpm range when going up long grades. Have not had a problem. I have done that with every rv or truck (different rpms for each one)that I have owned and did not run the temp up outside of "normal" range on any of them. So, in my opinion, you handled it just right.

For what it is worth, the chief mechanic at my rv dealership says to not run your tranny in economy mode when pulling hard. He claims that they have fewer complaints of over-heating from people that leave the trans in regular shift mode. I do not know if any of that is true, but I leave mine in "regular" mode all the time and have not had a problem with engine temperatures.
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Old 05-18-2006, 02:55 AM   #10
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Hi John (and others),

To echo (and clarify) what some of the others have suggested, the "mode" button doesn't really have any appreciable effect in most driving situations you are likely to encounter.

The possible exception being the exact issue you are experiencing.

If I understand correctly, the "Mode" simply causes the transmission to up shift earlier, in theroy increasing fuel economy.

This might be better regulated with your right foot, and your ears/eyes!

Most diesel engines don't respond like gas engines do in terms of how much fuel is being fed to the engine relative to the position of your foot on the accelerator. With diesel engines, the amount of fuel being fed to the engine has more correlation to the amount of "work" the engine is doing at a given rpm range. If you monitor the "engine load" display of your VMS (or equivalent) this explains why the engine load can be at 100%, despite the fact that you have only of the accelerator depressed. As the engine RPM's increase, the fuel being fed to the engine is decreased based on the accelerator position.

This is a long way of suggesting that the "mode" is more gimmick than anything else, at least for motorhomes operated primarily on the highway. Once you reach cruising speed, it has absolutely no impact at all. The only possible impact it might have would be delaying a downshift, and we see what effect that has (overheating). Having had many years operating large fleets of vehicles with Allison automatics, and trying every trick we could find to boost mileage, we came to the conclusion that the mode button is useless in vehicles like ours. If you read about other types of programming that the mode button can be used for, it makes more sense. Some applications (or vocations as Allison calls them) limit transmission shifting to certain ranges (say only gears 2-4) to reduce "hunting" for vehicles that drive in slow or stop and go driving, or that require frequent engine assisted deceleration. These are primarily in other "families" of Allison transmissions; however the touchpad controller is used more universally, hence the "less than useful" mode button. Some people I know suggest that the mode buttons real unspoken purpose in the MH series of transmission is to help reduce hunting, not to improve fuel mileage. Certainly, one could do a better job of controlling the shifting of the transmission with ones accelerator position, and most of us do just that once we have some experience.

As you might gather, we always leave the mode button off, and manually shift whenever engine load and conditions dictate. As it has been suggested, higher RPM's bring more cool air into the engine, move coolant, oil and transmission oil faster, and reduce internal stress. The cooling fan, being hydraulic, operates at whatever speed the controller dictates, mostly regardless of engine RPM's.

Thanks for indulging my somewhat overly detailed op ed!
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Old 05-18-2006, 03:59 AM   #11
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I have an 04 Journey that had the same problem. Several friends have had the same problem. We found it to be a dirty radiator. A mechanic told me the radiator is four inches thick and collects dirt due to the thickness. I used Purple Power from the local parts store. Used a spray bottle and once applied let it sit for several minutes before pressure washing it. I was blown away with the grease and dirt that came out. Now it runs cool even in 90 + degree weather going up hills with a trailer or van behind it.
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Old 05-18-2006, 04:16 AM   #12
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by rg:
I have an 04 Journey that had the same problem. Several friends have had the same problem. We found it to be a dirty radiator. A mechanic told me the radiator is four inches thick and collects dirt due to the thickness. I used Purple Power from the local parts store. Used a spray bottle and once applied let it sit for several minutes before pressure washing it. I was blown away with the grease and dirt that came out. Now it runs cool even in 90 + degree weather going up hills with a trailer or van behind it. </div></BLOCKQUOTE>

Indeed, in your chassis, this is a common problem due to the rear radiator configuration, and an oft misrouted engine crankcase vent tube. The oily vapors get caught in the rearward airflow, clinging to the radiator fins, and attracting dirt at a highly accelerated rate. The fouling that results from this condition reduces airflow across the fins, and results in diminished cooling ability.

Owners with the rear radiator configuration need to insure that it is regularly cleaned, as laid out in the maintenance guide.

Also, the mode issue and the downshifting practices remain the same across these chassis. Rear radiator chassis have a direct drive cooling fan, generally without a fan clutch. Increasing engine RPS's during periods of heavy engine load should help increase cooling significantly, provided the radiator area is clean as mentioned above.
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Old 05-18-2006, 04:43 AM   #13
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Hi Buck & Jeff - That's an interesting conclusion about the mode button. I went to an Allison seminar at an FMCA convention and they said to use the 'economy' mode. The tranny does shift up sooner to limit the engine at peak torque but your real-life experience in a fleet situation can't be discounted. I have never had to manage (manually shift) hill climbing before yesterday so I am a little puzzled.

There is a Freightlines Oasis dealer in Rapid City (20 miles away) and I'm going to stop in there today in the Jeep and chat with them. I'm now leaning towards the possibly of the coach having fan controller problems.

BTW - Jill at The Lodge says hi also
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Old 05-18-2006, 10:39 AM   #14
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Here is my two cents worth. Actually it comes from a trucker whom has been driving for about 60 years......he is 77. This is how he has explained it as I remember .

When climbing a grade the turbo is boosting the the intake charge at a high level of boost. That raises the temp, along with all the fuel being poured into the cylinders . Dropping a few gears lowers the boost, spins the fan faster and lowers the fuel being delivered . His advise to me when climbing a long grade is to downshift sooner and keep the RPM around 1900-2100. It has worked for us. High boost also increases EGT, also the reason for high temp, but most of us don't have that gauge. If I had that gauge I'd drive by the EGT temp, but instead I use the boost and try to keep it as much as possible below the max(24.3), when climbing the grades.
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