Coast Resorts Open Roads Forum: Class A Motorhomes: EXHAUST BRAKE PROBLEM
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 > EXHAUST BRAKE PROBLEM

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slickest1

canada

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Posted: 12/20/13 01:22pm Link  |  Quote  |  Print  |  Notify Moderator

Is your cruise control off. Sometimes that will affect the exhaust brake.


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slickest1

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Posted: 12/20/13 01:23pm Link  |  Quote  |  Print  |  Notify Moderator

sorry double post

ScottG

Bothell Wa.

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Posted: 12/20/13 01:45pm Link  |  Quote  |  Print  |  Notify Moderator

FRIZBEE1 wrote:

Scott, Brake won't engage at idle.


How does the switch feel? Same as always or is it kinda loose like it's worn? Either way, if you can short the connections to it either at the switch or at the other end of the wire going to it and it turns on then that sw is bad.


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DSDP Don

Moorpark, Ca

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Posted: 12/20/13 02:53pm Link  |  Quote  |  Print  |  Notify Moderator

FRIZBEE1......I've worked a lot on my exhaust brake because Monaco never wired it correctly and the exhaust brake flapper didn't engaged for years. I've read through your post and the responses several times and they are very confusing or I'm brain farting. The referral back to your first numbers of what happens is what's confusing.

First.....is this coach new to you and did this just start happening?

Second.....how do you know the exhaust brake flapper isn't closing if you can feel the transmission is downshifting?

Third.....Has your computer ever been updated to change how your exhaust brake works. Yours initially was designed to engage the moment you turn it on and your foot is removed from the brake pedal. Mine was the same and I later changed it to engage when the brake pedal was tapped and disengage when the throttle was tapped (computer change). When my exhaust brake switch is on, I can't use cruise control (different on newer models).


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yrusoslo

Myrtle Beach, SC

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Posted: 12/20/13 04:24pm Link  |  Quote  |  Print  |  Notify Moderator

I believe that motor had a optional engine brake, aka jake brake, thats the way I would have went, if I had ordered the MH.

wolfe10

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Posted: 12/20/13 04:33pm Link  |  Quote  |  Print  |  Notify Moderator

Yes, an engine compression brake (aka Jake Brake) was an OPTION on the ISL. Some manufacturers saves some $$ by doing an exhaust brake instead.

No idea the cost of an upgrade to the compression brake. May be that a PacBrake PRXB would be a good compromise.


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Executive

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Posted: 12/20/13 08:55pm Link  |  Quote  |  Print  |  Notify Moderator

Frisbee==I'm confused as hell...[emoticon]

Your synopsis as to how the EB is supposed to work is correct. What's confusing is what you are experiencing.

1. You said, Exhaust brake tests good and is lubed. How did you test it?
2. You said, Tranny downshifts but exhaust brake won't engage. but later you said it did not. Does is downshift or does the tranny pad light simply change to 4...??

The EB is a pretty simple device. That said, it sounds like maybe someone changed the downshift from 2 to 4. Both my Monaco's shifted to 2 but could be reprogrammed to 4. Don't know if that's what happened to yours or not. Do you have a foot pedal as well ??

Finally, my experience is that the original EB was pretty much junk compared to the PXRB. I switched mine out on the Dynasty and noticed a significant, and I mean a VERY significant change from the original..took me about 45 minutes in a campground with simple hand tools to change it out......good luck...Dennis


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FRIZBEE1

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Posted: 12/21/13 12:41pm Link  |  Quote  |  Print  |  Notify Moderator

Slickest1 Cruise goes off when switch is thrown.

Scott G Switch feels the same.

Diplomat Don. Had coach 10 yrs and issue is recent. I know when the flapper engages right after the tranny down shifts. I see the RPM go up and can feel the induced drag.

Dennis, The shop tested the EB on a stand alone 12V circuit and it closes. There is no foot pedal for the EB. Just a switch on the side panel. You mentioned downshift to 2 not 4. I may be mistaken and it might be 2. Even so it would not change the scenario in my original message, I don't think. Being 74 and well into the "Old Timers" think. I have trouble enough hooking up let alone changing the EB at a camp ground. Please give me some more info on what you did. My nephew is an aircraft maintenance manager. Maybe I could con him into doing it for a case of beer. Tks

DSDP Don

Moorpark, Ca

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Posted: 12/21/13 05:42pm Link  |  Quote  |  Print  |  Notify Moderator

FRIZBEE1......If you look inside the "run bay", outside bay under the driver's window, there is the large black box with fuses. Under that box should be two small black boxes that say "Monaco 1" and Monaco 2". Inside those boxes are a couple of relays that operate the exhaust brake, I would check those to make sure they are all good.

There is also an "Allison" box in that "run bay". I was surprised to find that that are about 5 relays inside that box, some of which control the exhaust brake.

Lastly, for some it can be difficult to tell if their exhaust brake (flapper) is actually closing. A sure way to tell is to watch your turbo boost gauge. When the flapper actually closes, the turbo boost will go to zero.

wolfe10

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Posted: 12/22/13 09:18am Link  |  Quote  |  Print  |  Notify Moderator

Other ways to tell if the exhaust brake is working:

Open window on side where exhaust exits. Drive along a road with wall. Turn brake on/off. You WILL hear a different exhaust noise if the brake is functioning.

OR, Drive down a road. Engage exhaust brake. Note what gear the transmission shifts to (not pre-select gear, but actual gear it is in at that road speed. Use the down arrow to "lock" the transmission in that gear. Turn on/off exhaust brake. Any additional braking HP will now be confirmed as the exhaust brake. No change, brake not working. Additional braking, brake working. Remember unless something like the PacBrake PRXB, braking HP at lower RPM is not that great. So testing at higher RPM will make it much easier to tell if the brake is working.

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