Exhaust brake not working

[captron33]

Cummins 400 isl 2006 travel supreme. About 90,000 miles. Need some help!
Thanks

[wolfe10]

As I posted above, one of the first things to check when the exhaust brake does not engage/transmission begin downshifting toward the "preselect gear", is the THROTTLE POSITION SENSOR.

If the sensor does not send the "throttle is closed" signal, the exhaust brake should not come on.

If you are not familiar with this, take it to someone who is. Having the wiring diagram for your system will save you time and $$$.

[captron33]

Reposting this. Stll not working.

[captron33]

Yes my coach has a exhaust brake.

[wolfe10]

Have you confirmed that you do have an exhaust brake.

As mentioned, the Cummins ISL could be ordered with either an exhaust brake, or for more $$ an engine compression brake (aka Jake brake). Also possible you have a VGT that acts as an exhaust brake.

Look at the exhaust manifold. If you have an exhaust brake, it will be bolted to the exhaust manifold.

Calling Cummins with your engine serial number would tell you exactly what you have.

Cummins 800-286-6467

[captron33]

Sorry,I don’t know how to do that. Traveling now near grand rapids,mi. For a couple weeks. I might give spartan chasis a call. Worth a try.

[wolfe10]

Did you verify that the throttle position sensor IS communicating that the throttle is closed???

[captron33]

Have not modified anything. I tried what you said to try. No change , not working at all. Was hoping some easy fix ….. like a fuse or cb. Very disappointed.

[wolfe10]

If the transmission shift pad does not change from "6" when you engage the exhaust brake, it is not working. That is one of the first step. When the brake was working for you, what was the pre-select gear/what gear did your shift pad change to when you engaged the brake?

Verify that your throttle position sensor is closing when you get off the throttle, because any throttle will cause the exhaust brake to not engage.

Again, a little confused as the 2006 Cummins 400 HP was the ISL, not ISC. Have you modified your ISC for more HP?

[captron33]

Sorry, yes isc 400. When i activate the switch on my left , the light on the dash ( aux. brake ) doesn’t come on and no down shifting or drag is created. I will try what wolfe said. Thanks for the suggestions.

[larry_cad]

wolfe10 wrote:

And, very easy to verify if any type of engine brake is working: Use transmission down arrow to select a gear where you are close to the upper end of the RPM range. Turn engine brake on/off/on. Since the transmission is now a constant, easy to see if you have added braking HP.

Brett, thanks for that suggestion. Never thought of that.

Larry

[wolfe10]

Probably need some clarification.

Cummins 400 HP generally means the Cummins ISL. The ISL could be ordered with either exhaust brake or engine compression brake (for more $$).

If Cummins ISC, it will have an exhaust brake.

Let's see how far into "engine brake is on" you get: Does the Allison shift pad change from "6" to the lower gear programmed as the engine brake pre-select?

What brand of exhaust brake do you have. If PacBrake, has it been lubricated:https://pacbrake.com/product/c18037-superlube/

And, very easy to verify if any type of engine brake is working: Use transmission down arrow to select a gear where you are close to the upper end of the RPM range. Turn engine brake on/off/on. Since the transmission is now a constant, easy to see if you have added braking HP.

[larry_cad]

Curious to know how you determined that exhaust brake isn't working? If the brake in your coach is activated with the dash switch, it will close automatically when you begin to slow down. Typically, this will also cause your transmission to downshift to a lower gear, (typically to 3rd) The actuator for the brake is an electrically operated solenoid that pulls the brake valve closed. I believe you also have a Cummins ISC engine.

The problem with determining it is not working, is that it only activates when you are slowing down, and then you have to visually see the solenoid action. That is not an easy task. To see mine work, I have to raise the mattress, and open a hatch while the coach is driving. This requires a second person to watch while I drive.

You can test the operation of the valve by applying 12VDC to the solenoid wires, while not moving, but that doesn't guarantee that the 12VDC will be applied when driving.

You also have to periodically lubricate the valve mechanism which special exhaust brake lubricant. This will insure that valve mechanism is free to move. They are known to get stuck from rust. You can test the mechanical operation with your hand by turning the operating mechanism to verify it opens and springs closed when you let go.

[haste_maker]

Could be many things...first I would check the switch on the foot brake pedal...on 18 wheeler trucks that I drive dirt/water can get in the switch and cause it not to work.