Cool running Cummins

[dshogman]

I need someone to tell me if I have a problem: since I bought the coach in early 2007, the engine temps have always been in the 195 to 203 range depending on the terrain etc. Sometimes dropping below 195 even. I noticed a day or so ago, that the temp was running from around 185 up to 193. Outside temps in the high 70s to mid-80s. Mostly smooth and relatively level terrain - coming down through Virginia and North Carolina.
Any thoughts?
Thanks.

OK, OK, OK - I just read Mike's discussion in the latest newsletter, and YES, I have been running the air conditioning almost continuously. So that must mean the cooling fan is running on high, and the engine temps are lower than normal.
Is this correct??

[SteveS]

David - My temps run about the same with or with AC running. The coolant thermostat seems to keep it around that temp. It runs at 205 - 220 when pulling a load up a long grade in 100 degree outside temps.

[Renipladlo]

All - my normal temps are w/o toad mostly level terrain is: 185F, and as high as 195F when pulling a long hill.

When pulling the toad the temps are between 5-10 degrees hotter under the same conditions.

So I think based on that you are right about where you should be.

My A/C seems to have little to no effect on my engine temps as far as I can tell.

Also remember check the coolant reservoirs when engine is HOT!!!

[Dale777]

When pulling my 2006 Jeep Grand Cherokee toad, my temps are typically 188-199, unless I pull a long grade on a hot day. On short or gentle grades, the temp will always move up near or at 199 until I top the grade.

For the long grades on a hot day, the temp will be about 10 degrees warmer. I've never had it above 110. When it gets near 110 on a long grade, I manually downshift to 5th or 4th, which cools the engine down. The dash A/C seems to make no difference. I always pull a toad, so I don't what the temps are without it.

[bigfish]

The engine temps on for our rig while towing is 193-196 deg F unless pulling a grade, then it may work up to as much as 205 deg F. Temps don’t seem to be affected by use of dash A/C. Transmission temp will normally stabilize @ 210 deg F, unless operating in some slow traffic or while descending a grade where temp may creep up to as much as 224 deg F. While ascending a grade transmission temperature my go down to 205 deg F, sort of counter intuitive.
BTF

[Dale777]

Originally Posted by Dale777

When pulling my 2006 Jeep Grand Cherokee toad, my temps are typically 188-199, unless I pull a long grade on a hot day. On short or gentle grades, the temp will always move up near or at 199 until I top the grade.

For the long grades on a hot day, the temp will be about 10 degrees warmer. I've never had it above 110. When it gets near 110 on a long grade, I manually downshift to 5th or 4th, which cools the engine down. The dash A/C seems to make no difference. I always pull a toad, so I don't what the temps are without it.

CORRECTION:
In my note above, I said, "I've never had it above 110. When it gets near 110...".

I meant to say, "I've never had it above 210. When it gets near 210...".

[kraig]

When I got my Alpine, I also wondered about my coolant temp. also. I called Cummins tech support 1 800 Diesels or 1 800 343 7357, give them your engine serial and they will give you your operating range. I would also ask them are there any critical updates for your engine that haven't been done. I do have a different engine than you, they told me I could go up to 225 degrees. I also manually downshift going uphill, and keep it down to about 200 degrees.

[Renipladlo]

In thinking again about this thread. The only time my engine has crossed the 200 degree barrier was when we were crossing over Governmnet Camp in Oregon on US 26. Once you leave Welches, OR heading east, the incline increases, we were in 4th gear, holding around 30-35 w/toad, and we hit 217, the caution buzzer sounded, and I pulled into the Ski Bowl parking lot to let it cool down. Reaching that temp could have had something to do with it being around 95 F that day. It took less than one or two minutes for it to get back down to 185, and then we took off again. Once in Florida on a very hot day I think I hit 199 for a while. It only takes a couple of minutes to get it to cool off once we stop and let it idle. I think I have one of the good cooling systems as others have remarked they have some issues.

[RickO]

I don't think you're far off. I've never checked the impact my dash a/c makes but we nearly always run it and tow a Ford Explorer. Typical temps on level interstate are 185/190. On long hard pulls with the toad (I70 in Colorado) I really drive by the temp gauge and down shift to keep the RPMs near 2K and the temp below 215. That has only been an issue in very hot weather.

[Renipladlo]

As you don't own an alpine with our setup, my comments below apply mostly to that configuration, but it's assumed your coach has the ISL/ISC or ISCe engine. If it is another engine like a CAT, or Detroit Diesel, I don't have any information concerning it and my comment is not applicable.

Ok - On page 1-18 The Cummins ISC-ISCe & ISL manual states this caution.
"Do not operate the engine at full throttle operation below peak torque rpm (refer to engine dataplate for peak torque) for more than 30 seconds. Operating the engine at full throttle below peak torque will shorten engine life to overhaul, can cause serious engine damage, and is considered engine abuse”. Based on what I think it the torque peak RPM, you should be doing ok, but 2K RPM to me is way to high, based on redline.

I believe the ISL/ISC class engines reach peak torque at around 1300 RPM, but don't quote me on this. If you check you tach at 60MPH and in 6th gear you should be turning around 1550-1600 RPM, which would be the normal RPM target range for all gears under normal load. The maximum sustained RPM is 2300 RPM (I think, but cannot find my reference to that number), if you are running up the hills pushing 2000 RPM I hope you have not damaged the engine. I believe 4th gear and no more than 1500-1600 RPM are considered the safe limits. Occasionally you can take it up to 2100 RPM but not for any sustained operation. It is assumed that sustained operation would be in excess of 30 seconds as stated above. When I have passed vehicles and am clicking along at 75MPH for a bit to get around them, my tach hovers at 1800-1900, but it’s not for longer than 30 seconds, and I slow down once around them. I watch my RPM's and engine temp in conjunction with long pulls with the toad. If either get out of my safe zone, I slow down or shift to a lower gear, and not going above 1900 RPM period.

My manual does not state normal operating rpm range, max RPM range (red line), and I could have sworn it's someplace. I would think twice about running the engine that high climbing a hill.

Again, my caveat would be, if it’s not Cummins as stated above, ignore what I said, and I cannot find my data nor have I looked at the data plate recently. What that reminds me to do is, make a picture of it, blow it up in size, and put copies in both manuals-home and coach so I have it.

[RickO]

Thanks Monte. Looks like I've got some homework to do and a call to Cummins will probably be in order. I have a 2007 coach with ISL 400.

The practice I described came directly from the Cummins tech in Bakersfield following a 40 mile tow off the Grapevine leading to Los Angeles. It was my maiden voyage and got a "Stop Engine" condition. Following 40 minutes on the phone with CoachNet they sent a tow truck to bring me back to the Cummins shop in Bakersfield.

Turned out to be a silly false alarm triggered by a somewhat low coolant level exaserbated by going up the hill but the tech took the opportunity to stress to me that on long pulls (especially when towing) I had to keep the RPMs up around 2000 to keep the fans turning fast enough to cool properly.

Thanks again...

Rick

[Renipladlo]

Hmmm, my guess is the fans are controlled either by hydraulic or electric and actuated by a the thermostat and a controller, but again I am not familiar with your cooling system. So that info from the Cummins guy might be in error. I have not seen a direct drive cooling fan on a motor home except in Class C’s and even those have clutch fans or electric cooling fans.

The thermostat is connected to the controller which starts the fans, and regulates their spin rate based on the engine temperature. And ours have a vansco electric management system, so that plays a part in it as well. You can get sort of an explanation of it if you go to the Alpine Coach Association and read the September 2010 Newsletter. Our resident Famed “Engineer Mike” wrote a great article on the types of controllers we have on our alpines. Our fans are run by a hydraulic pump system.

And on Alpines, our coolant tank is at the back of the coach and we have discovered to always check the little coolant level window with the engine warm. That in and of itself goes against everything I have ever been taught, but with the metal reservoir tank, and the little window not being tapered, when it cools the coolant seems to hang in the window and you assume it’s ok, when in fact it might be low. You then add coolant and it's all over the ground, so Alpine owners have learned to check the level with engine warm, and then if the window is empty, you add some, ensuring that you take the cap off real slowly so you don't get burned. I have never gotten a low coolant light, but as I understand it the sensor is in the lower 3rd of this tank I speak of.

When you talk to Cummins please post the information here, because I have asked the questions in the Cummins forum or red line, operating range RPM, and stuff such as that, because my manual does not provide it. I was going out to the website to see if I can find it there, but have not made it yet.

Happy Camping.

[takepride]

Hmm. I've been told and have repeatedly read that when climbing, it is best to down shift to achieve 1800 to 2000 rpm, keeping the temperature in range and the power at maximum.

In practice, climbing the various hills out of the LA Basin, that recommendation always works. If the rpm's are at normal (1500), the temperatures skyrocket, every time. My coach is under-weight, but it won't climb out of the Basin at 75. Besides, I'd never allow it to. It will do 55, towing and maintain 210 degrees or less, if I keep it at 2000 rpm.

Your manual quote says:

"Do not operate the engine at full throttle operation below peak torque rpm (refer to engine dataplate for peak torque) for more than 30 seconds. Operating the engine at full throttle below peak torque will shorten engine life to overhaul, can cause serious engine damage, and is considered engine abuse”.

That would mean don't have it floored if the rpm's are below the peak torque, not above the peak torque. In other words, don't lug it. Keep the rpm's up.

Of course you don't want to over rev the engine either.

[Old Scout]

Not sure what the "red line" is on the Cummins but assume excessive RPMs or lugging the engine over an extended period are probably not good. Given the complexity of the EMS on the Cummins, I would like to think the EMS would derate the engine before reaching a "red line" condition--that's not to say you still cant abuse the engine. Memory is a precious thing but it seems like max torque was at 1300 and max HP was at 1800 rpms.

As for proper RPMs, I recall an early gearhead session with Mike Young from Yakima Cummins. Back then, the ISL 400 was a relatively new feature on Alpine [yup--along time ago]. He had two cautions for this "new" engine: 1) shift down to keep the RPMs up on long up hill pulls [perhaps 1800-2000 rpms]. The ISL has plenty of HP to pull but needs RPMs to keep the fan at speed to cool [engine RPMs determines hydraulic pump flow and ultimately fan speed. 2) Becareful when using the Jake brake on wet/slick pavement--the ISL has lots of braking HP.