Author Topic: Exhaust Brake Issues  (Read 15691 times)

Doug Birch

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Exhaust Brake Issues
« on: October 19, 2008, 09:51:47 PM »
We have a 42' 2007 Contessa with a C9 400hp and are having issues with the exhaust brake (Jacobs) holding the coach on 6% or grater down grades. The GCVW is just under 44,000# which is under the GCVWR. I have had Monaco check exhaust brake out and they said everything including back pressure are within spec's. We have tried starting out in 1st gear and it doesn't make a difference, we still have to use the brakes to a point that they start getting hot and you can smell them, seems mainly the front disc brakes. Is anyone else having this issue and have you found a solution for it.

David Rudisill

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Re: Exhaust Brake Issues
« Reply #1 on: October 20, 2008, 12:51:18 AM »
I assume that you really did mean that you have an exhaust brake, not an engine compression brake.

We have an '04 Monterey. Previously, we had an '03 Santiam. Both use the Pacbrake exhaust brake.

In neither case will the exhaust brake hold the coach on a 6% grade, and both of these coaches are substantially lighter than your Contessa. You need a real two-speed engine brake to get that kind of engine braking.

On our Monterey, if I use the service brakes periodically to keep the rig from shifting up to fourth gear (around 50 MPH), the exhaust brake does a satisfactory job on 6% grades. Once it shifts into fourth, the engine speed is too low for the exhaust brake to work enough to matter.

Hope that helps.

LEAH DRAPER

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Re: Exhaust Brake Issues
« Reply #2 on: October 24, 2008, 08:51:07 PM »
Isn't anybody GEARING DOWN instead of relying on the exhaust brake to do all the work?  If you are not then you have more guts than I,

Richard And Babs Ames

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Re: Exhaust Brake Issues
« Reply #3 on: October 25, 2008, 12:31:18 AM »
Most exhaust brakes are programed to down shift the transmission. With the Allison either second or fourth gear without letting the engine over rev. IOW down shift is automatic and the exhaust brake, transmission and engine work together to slow down the coach. If you only go 4th get reprogramed to 2nd gear.

Robert Mathis

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Re: Exhaust Brake Issues
« Reply #4 on: November 02, 2008, 01:19:38 PM »
I also have a 42 Contessa and have the same problem. I am taking mine in next week (I hope) to have Cummins look at the settings on the pacbrake. It seems to me that it isn't working as well since they replaced the engine that blew.

Phil Sales

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Re: Exhaust Brake Issues
« Reply #5 on: November 12, 2008, 01:37:35 AM »
On turbo charged diesel engines, gearing down,only works when accompanied by an engine brake of some type. These engines do not make back pressure like the N/A  (naturally aspired) diesels used to do and gassers still do. Hense the development of the Jacobs and other engine brakes. But try to tell the old guys why your brakes are hot, they don't believe you. LOL   Phil

Ken Sair

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Re: Exhaust Brake Issues
« Reply #6 on: November 18, 2008, 12:52:19 AM »
We have a 40 ft. Contessa (2007). Ours also would not hold the coach back at any speed. Turned out it wasn't plugged in and was not working at all. After having it fixed it works very well. However, it requires an assist periodically from the service brakes to prevent speed build up on grades over 6%.

Its pitiful engineering to save money. A similar coach (Monaco Windsor) in 2006 came with a 2 stage engine brake. Drove one, WOW, like throwing out an anchor. Monaco in their infinite wisdom felt the exhaust brake was 'adequate' and went with that instead of the engine brake to save money. I know, I argued long and hard to get the engine brake to no avail.

These coaches need an internal engine brake, not an exhaust brake. Monaco got it wrong in my opinion.
BAC members since 2006

Richard And Babs Ames

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Re: Exhaust Brake Issues
« Reply #7 on: November 18, 2008, 01:58:51 PM »
Ken I do not know about Cummins options but CAT only offers the Jake Brake (engne) braking on its larger engines or C13 through C15. The C 7 and C 9 only have the exhaust option available.

 Recent redesigns such as Pac Brake's http://www.pacbrake.com/index.php?page=prxb-exhaust-brakes-2 and others offer better breaking preformance than the previous models. You could consider an upgrade to a newer technology exhaust brake system.


We find the original Pac Brake on our '97 preforms well as does the on on my son's Jayco Seneca with the Chevrolet Diesel engine as a suppliment only brake and our chassis service brakes have over half the disc brake pads left at 103,000 miles.



MarcRodstein

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Re: Exhaust Brake Issues
« Reply #8 on: November 21, 2008, 05:01:16 AM »
Using the exhaust brake on a steep descent requires an understanding of how it works, and the proper technique. The exhaust brake is most effective at RPM's over 2200, but if your speed and RPM's build up above 2500-2600 RPM, your transmission will automatically upshift, which reduces your rpms and greatly reduces the effectiveness of you exhaust brake. For downhill control, periodically apply your service brakes to keep the engine RPM's below 2500 so as to avoid an upshift. You want to use the service brakes enough to control the engine speed, but not so much as to overheat the brakes. On an extreme downhill slope of 7% or more, start down in 2nd gear and use your brakes intermittently in order to keep the transmission in 2nd gear.  This requres descending at reduced speed (put your flashers on), but is much safer. If you allow the transmission to shift into 3rd or 4th gear, your braking and speed control will be greatly diminished.

Phil Sales

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Re: Exhaust Brake Issues
« Reply #9 on: November 21, 2008, 02:13:13 PM »
Ken, I'm not sure which engine you have, but the C-7 and C-9 will not support the full Jacobs compression brake. It's not an available option for those engines. I have the older Cat 3126 HEUI and I can't have one on my engine either. But would love to have one because they are exponentially more effective.  The exhaust brakes are better than nothing though.