Erratic engine brake engagement

[Learn2Q]

My 2006 Travel Supreme Select has a big red 500 hp Cummins engine. I'm sorry, but I don't know much more about the model. This is my first coach and my first RVing experience. I'm full timing it.

My engine brake, when it works, works like it should. Sometimes, it just won't engage and doesn't work. Any ideas other than taking it in to a Cummins facility?
thanks,

[Ann n Gene]

I THINK that you have a Cummins ISM engine (that is what my 500hp 2007 is) and I would really recommend that you take it into Cummins, not something to let just anybody tinker with.

[J Walker]

You can look for a loose connection or a bad switch and I would do that, but Ann n Gene are right that it gets very complicated after that. My exhaust brake was not working when my rig was new and two shops took about six weeks to find and fix the problem. The engine and transmission ECMs are involved in the brake. After all of that they found a wire that was cut during manufacture.

[H. Miller]

Might also try the high temp turbine lube on all the moveable parts & joints. Owners manual is elsewhere but recall this needs to be done more than just annually. Available at most any trucking facility or diesel engine mfg.

[Gary RVRoamer]

Are you aware the engine brake will not function if the cruise control is on, or if you are pushing the accelerator pedal at all?

You also will not feel the brake much at all if the speed is high and the transmission is high (6th) gear. he brake forces the transmission to select a lower gear (usually 2nd), but you don't get much brake effect until it slows enough to get at least to 5th gear.

[Perry White]

My engine brake works with the speed control on. If I'm going down hill it comes on about 4 mph above set speed.

[Steve Ownby]

Troy,

Another full timer here and a driver with the Cummins ISM. It's truly a great engine for a motorhome and the Allison 4000 transmission make for an outstanding drive train.

A previous poster mentioned speed. He is correct that if you are in 5th or 6th & your rpm is too high for a kick down then you don't feel much retard. Look at your shift selector. When the brake engages the selector will display 3 which is the default setting for the compression brake. Also make sure the rocker switch is set to the high position & you will get the strongest braking effort as it uses all 6 cylinders.

That being said. When I bought mine the Jake was not working. I took it to Cummins and the act of troubleshooting fixed it. It has worked fine ever since.

Is there a website that gives the BBQ circuit you travel. If I'm in the area I'll come root for you.

[spike45]

500 HP and red = ISX. The ISM may have 500 HP but is painted black when it leaves the Jametown, NY Cummins plant.

[spike45]

Quote:

Originally Posted by Learn2Q My 2006 Travel Supreme Select has a big red 500 hp Cummins engine. I'm sorry, but I don't know much more about the model. This is my first coach and my first RVing experience. I'm full timing it. My engine brake, when it works, works like it should. Sometimes, it just won't engage and doesn't work. Any ideas other than taking it in to a Cummins facility? thanks,

Have you read your Engine Owners Manual section on using the Engine Brake Control? There are a number of switches but first be certain that you are trying to operate it within the parameters that it operates under. The O&M guides on Cummins engines are quite extensive with good information. If after you are certain that you are operating the engine brake in accordance with the manual, then go either to Cummins distributor or any Cummins authorized OEM truck dealer who can check out the ECM, switches, etc.

Apart from fixing some obvious things, generally troubleshooting by parts replacement is expensive and may not fix anything. Buying a diesel MH and learning mechanics is doing it the hard way and may be very costly in blunders. As I read on the Caterpillar forum, someone was adding an exhaust pyrometer to his engine. Why he chose to drill the exhaust manifold where he did is unknown. But he has a deep hole in a very expensive piece of cast iron and even more expensive to remove and replace and still has not broken through to the exhaust. Unless you are experienced in diesel mechanics it is not like fixing your car.