Cummins 370

[JC2]

Will be looking at a 2001 HR Imperial with the ISL 370 Cummins, 60000 thousand miles, sometime towards the end of next week. Having owned different rvs over the years, I am somewhat confident in what to look for when purchasing a used unit. My main qestion at this time is about the engine. Is the engine in this unit generally considered pretty reliable and bullit proof or his it known to have recurring problems. I've owned a 2001 Dodge dually with the cummins and a 2003 Dodge 250 with ho cummins and was impressed. I realize this engine in the mh is different so the reason for my question. Thanks in advance.

[Mr_D]

Some of the ISL's had wrist pin problems, but they all "expired" before about 15,000 miles, so you should be good to go.
Does it have the engine brake or exhaust brake? The 370 came either way depending on how the MH manufacturer spec'd it (and paid extra for the engine brake)

[JC2]

Thanks Mr_D

This one reportedly has the engine brake. (Good or bad vs the exhaust brake?) One thing I forget in my originally post was the type of fuel pump in this engine. Does it have a lift pump, which were bad about going out in pu's, or do they have maybe an electric fuel pump.

[RandD]

Hi Jerry,

Sounds like an interesting find. An engine brake is what every exhaust brake wants to be ;-) Since they use engine compression instead of exhaust back pressure, they are quite a bit more effective. I wish I had one instead of the exhaust brake I have, but that was not a selection criteria.

Let me know how your inspection goes!

[Steve Ownby]

The wrist pin problem was with a small number of engines built in the 05/06 time frame so you have no worries there. I'm sure an ISL in a high level coach like an Imperial will have the Jake compression brake which is a 2 stage internal engine brake which provides more braking power than an exhaust brake.

The ISL does have a lift pump as well as an injector pump but I don't believe it has a history of early failure. The miles are obviously low but there have been a number of maintenance cycles since that coach was new.

If maintenance records are available, make yourself a chart and go over the critical driveline items in detail. Make sure the lube/oil/filter service has been done on time, meaning annually even with low mileage. The transmission was shipped with Dex III which is no longer supported or recommended by Allison. The transmission service schedule with Dex III called for fluid/filter change every 12 months and it was very rarely done on time. If Transynd is not currently in the transmission, be aware that it is an expensive change over and you should build it into the purchase price. If you have the time and inclination, an oil & transmission fluid analysis will provide piece of mind.

Good luck & let us know how it turns out.

[Mr_D]

Originally Posted by JC2

Thanks Mr_D

This one reportedly has the engine brake. (Good or bad vs the exhaust brake?) One thing I forget in my originally post was the type of fuel pump in this engine. Does it have a lift pump, which were bad about going out in pu's, or do they have maybe an electric fuel pump.

Much better to have an engine brake! Wish our ISC did but they didn't put them on that small and engine.

[JC2]

Good info so far. Keep the advice/tips coming.

[spike45]

You want bullet proof? The ISL is not your engine. Anytime you wring more HP from less displacement you are stressing the engine. The ISC is more forgiving than an ISL. The most bullet proof engine is the ISM at 11 liters but similar HP ratings to the high end ISL. ISMs are found in some line haul tractors in fleets. ISL is not.

[Steve Ownby]

Spike45,

As the happy owner of a pre-EGR ISM, I couldn't agree more. I'm closing in on 90K trouble free miles with a lifetime mpg of just a hair below 8. This includes usage by the generator and AquaHot, so my over the road mpg is somewhat better. Cummins, decided not to up date the fuel system on the ISM to meet current EPA requirements so the perfect motor home engine is no more. They replaced with the ISX light which is about one liter larger and about 800 lbs heavier than the ISM. I don't believe any Motorhome builders are using the smaller ISX as the 15 liter ISX is the same weight with substantially more hp & torque.

I will be holding onto my ISM powered coach for as long as I can still drive it.

[Perry White]

The new Newmar Essex has the new ISX 11 ltr I believe. And your right, ISM EGR isn't nothing but problems for me. 6.4MPG for me.

[zmotorsports]

Overall the ISL is a good engine whether the 370 hp or the 400/425 hp versions. I prefer the pre-2008 model year due to less emissions crap, ie. EGR and DPF and later models, urea. I also prefer the engine compression brake to the exhaust brake. It delivers ~345 braking horsepower @ ~2300-2400 RPM which slows our rig down even when towing 10k+ pounds of trailer.

There was some wrist pin issues in 05/06 model year engines but most have been addressed and where you are looking at a 2001 that wouldn't apply anyway.

Valve adjustments are not needed until 150k miles, although I did mine last year, so it is not an expensive engine from a maintenance standpoint.

I did replace my lift pump back in 2008 due to a leak but that was mainly due to the removal of the parafin when they switched to the ULSD diesel fuel.

The Imperial is a nice coach, it is basically the equivelant to the Monaco Dynasty such as ours and I have been very pleased overall with our coach.

Mike.

[Gary RVRoamer]

I have the 370 ISL with the Jacobs two speed engine brake in my 2004 American Tradition. The engine is actually a 2003, so probably the same one you are looking at. It has been a very sound engine - zero engine repairs so far (only 64k miles though). I do not agree that the ISC is more reliable - the ISL is an 8.9L engine, so it is not being stressed to produce extra horsepower versus the smaller ISC (8.3L). The 370 hp version of the ISL is loafing - the same engine produces 400 or 425 hp effortlessly.

Mine has an electric lift pump. I think all the electronic engines do - mechanical lift pumps were used in the pre-electronic models.

[Smitty77]

Playing a bit of catch up on my normal checking into the Cummins section!

I too have the ISL370, but with much less miles then Gary (Plan to work on this over the years ahead, and play catch-up!!!), having just clicked over the 20K recently - but also with no problems.

When Spike45 posts, I read (as with Gary too), so I was hoping he could expand on his comment about the ISL in relation to the ISC.

I understand the reliability of the ISC, a solid engine from all that I have read. It also seems to have many more upgrade paths for chips, Banks, etc. Then the ISL. The ISC did come in some larger 40' coaches, but were usually a bit undersized for the the job of moving a 40' around. (Thus many have added the extra power of the chips and Banks.) Not a dig on ISC.

As Mike posted, the ISL is a good engine too. Concur with noted problems.

It seem when you get to the 40' plus range coach, that the ISL and the Big Blocks above that, are better suited (on the Cat side, the C9 seems to match with the ISL the closest.). Many manufacturers used the ISL in their mid level coaches, saving the Big Blocks for the more expensive units. Quite often the more expensive units require the Big Blocks, due the extra weights of all the goodies. Thinking of like Executive vs Diplomat from the Monoaco line, and say in my case the Allure vs Magna/Affinity in the Country Coaches. But the other reason they spec the bigger engines, is as a sales differentiation between lines. Yes, on some of the upper middle coaches, engine options were available like the Intrigue in some years could be purchased with a Big Cat as an option.

And to Steve's input to this thread - yes, I'd have preferred the ISM in the Allure - but it is what it is! I did look real close at a few Foretravel's, like them quite a bit. With the U295 being more to my likes then some U320's, as they had less glitz. ISM's were in many of the Foretravel's we looked at. But this is a case where the inside was more important then the major plus the ISM and Retarder had in my scoring sheet. The wife wanted a Big Galley, and the Foretravel's always seemed to have a smaller to medium size galley.

As Gary, I and others have posted on other threads, it would be great to get just a bit more out of our ISL370's - but so far have not found away to do this that does not have too many downside risks... (propane and other injections; and no chips seemed to be available that I can find; when I called Cummins with my engine number, they said it was not re-flashable to 400, etc.)

OK, I rambled (it's Sunday, and I allow a bit more laziness in my mind functions then normal!), but I'm interested in Spike's comments in general about the ISL as not being bullet proof. In the 40' plus size, is not an ISL going to give you better life then a harder working ISC? (And yes, exclude the wrist pins in this, as that was an isolated group of engines. But great, if that is the reason for the non bullet proof comment, I could understand that as taken in the context of ISL's in general. But for the thousands of units with no wrist pin concerns, is the ISL a problematic engine? My research made me comfortable with the ISL 370, did I miss something?)

Best to all, be safe, have fun,
Smitty

[spike45]

Originally Posted by Gary RVRoamer

I have the 370 ISL with the Jacobs two speed engine brake in my 2004 American Tradition. The engine is actually a 2003, so probably the same one you are looking at. It has been a very sound engine - zero engine repairs so far (only 64k miles though). I do not agree that the ISC is more reliable - the ISL is an 8.9L engine, so it is not being stressed to produce extra horsepower versus the smaller ISC (8.3L). The 370 hp version of the ISL is loafing - the same engine produces 400 or 425 hp effortlessly.

Mine has an electric lift pump. I think all the electronic engines do - mechanical lift pumps were used in the pre-electronic models.

Gary,

You look at this matter from the end user point of view. I look at it as a retired field service engineer for Cummins. ISL at 400, 425, 450 is more stressful as compared to producing the same HP from 11 liters in an ISM. I can assure you that an ISL can be made to produce 600HP.....but not for long.
The ISL is popular as it produces high HP ratings in a supposedly low duty cycle application (MH). It is compact and reduced weight compared to the ISM. But is it NOT as reliable as the ISM due to HP per cubic inch. You remember the old saying, "there is no substitute for cubic inches." That WAS true until electronic engine controls.

For those who are not aware, you had better take really good care of your engine coolant if you use coolants that have supplemental coolant additives that require periodic replacement such as a coolant filter at oil change time. I have seen some pretty sorry looking ISL and ISC cylinder liners from engines that had poor coolant maintenance. With the low "block-to-liner" clearance of these engines, they are more susceptible to cavitation pitting. ISM is not as the HP density is less and the liner clearance is greater.

For the rest of you who want to put chips in to produce more HP or add Banks turbos for more power, please send me your serial numbers so that if I should decide to buy a diesel pusher, I WON'T buy yours!

Those time bombs are costly to repair and the removal and installation costs are greater in your MHs than in a truck.