Is my exhaust brake working?

[Frederick Thornton]

Hi everyone, here's the background: I have a 'new to me' 2007 Beaver Contessa Bayshore with the Cummins 400hp engine. I bought the Beaver in February right before Covid-19. Being new to diesel RVs, I thought the engine and exhaust brake were fine. With eb switch on, the transmission would downshift when accelerator was released and the coach would slow down. In late June, we went on a trip to Colorado from Dallas area. I noticed that the exhaust brake would not help much on long grades and engine would run up to about 2500 rpm. Leaving Santa Fe for Creede, CO, there was a steep grade and I had to use the air brakes to slow down because the eb wouldn't hold the speed. This made me start thinking the exhaust brake was not working... I found a truck service business that agreed to take a look, and the service guy took about 10 minutes and said I had a blown #4 exhaust gasket and that was the problem with the exhaust brake. We went home because I could not find anyone within 200 miles that had time to work on the problem including this guy.

I have just gotten the coach back after getting the exhaust manifold replaced (plus some other stuff $$$!) at a truck repair center. Around flat Dallas, I can't tell much difference in how the eb slows the coach and I thought I would. I believe the truck service center checked everything about exhaust brake function while they had the engine apart, and they drove the coach after putting it back together. I know the exhaust leak is fixed, but could there be yet another problem?

Here is my question: How do I 100% verify that the exhaust brake is really working? Should I have someone in the back look through the access panel in athe closet to watch the actuator when I let off the accelerator? Or is there something else I can do to verify it works?          Or am I being paranoid? (I am! :-)

Thanks!

[Dave Atherton]

Frederick, in answering your questions may I add on some Cummins ISL engines are equipped
With what is called an exhaust brake of which sounds like what you have just had spent a ton of
money on. Than Cummins ISL 400 are equipped with a engine compression brake which is a
complete different system . To explain this further an exhaust brake has a flapper that operate
off of air pressure and effective of at speeds 45mph or lower and is connected to the exit end of
your exhaust manifold ( this is why the manifold gasket blown and braking was not fully effective.)
Now going with a engine compression brake operates off the engine valve train in some engines
Have 3 settings and some engines have 2 settings to give you braking effective on grades.
Dave Atherton Retired Cat Mechanic

[Frederick Thornton]

Hi Dave, yes this is an exhaust brake that closes off the exhaust after the exhaust manifold. Are you saying that it only helps at 45 mph or slower? I saw where you posted a document about exhaust brakes a couple of years ago but I couldn't find it. Could you point me to it?
Thanks!

[Dave Atherton]

Frederick, maybe Steve can find this for you in ask Dave. One thing that I might add and you can look this up. Exhaust engine brake brake operating flapper that is air operated holds back engine exhaust
Pressure that slows engine. The reason I mention the exhaust brake does not operate effective with
engine speeds above 45mph, the exhaust pressure exiting the engine exits out the exhaust manifold
That connects the exhaust brake assembly ( the engine pressure will overcome the air pressure that
holds the exhaust brake closed will not hold the flapper valve in the closed position and overcomes
a preset spring in the air cylinder till you reduce speed.)  Last with your Cummins 8.3 engine you do not have a VG turbo
charger and your turbo charger has a wastegate and flapper.  Dave Atherton Retired Cat Mechanic

[Steve Huber Co-Admin]

Fredrick,
With the exhaust brake on, drive the  coach at about 45 or so and then remove your foot from the throttle.  If working, the tranny should downshift and the coach should decelerate.
Steve

[Frederick Thornton]

Hi Steve, the coach has always downshifted with eb on, even with the blown exhaust manifold gasket. The question is how quickly it should slow down... The various service people have said a blown exhaust gasket would decrease the effectiveness of the exhaust brake because the back pressure would be less in exhaust system, thus reducing the eb engine braking... Since I have no experience with an exhaust brake and since the breaking before and after the exhaust gasket replacement seems about the same to me, I am wondering if the valve that blocks the exhaust gases is working. I think I'll get someone else to drive, I'll get in the back with the engine access panel removed, and observe to see if the valve is moving. If it is, then all is well. If not, then I have a different problem!

[Bryan Beamon]

Frederick, on our 07 Contessa with a Cat C9 exhaust brake we experienced a warped exhaust housing on the exhaust brake which decreased the effect of the exhaust brake and caused an engine over rev of 2800 rpms. The Jacops exhaust brake was replaced with a new Pac Brake that solved the problem

[Joel Ashley]

Keep the mechanism working with Pacbrake lube.  Don’t use just any lube that’s not up to the turbo/manifold heat.

https://pacbrake.com/product/c18037-superlube/

Exhaust brakes are commonly called “Pacbrakes”, even though on many of our coaches they are built by Jacobs Engineering, the builder also of compression brakes, aka “Jake Brakes”.

[Bryan Beamon]

Joel ,Jacob's no longer makes exhaust brakes and only Pac Brake made a replacement for our coach. That is why we had to switch to a Pac Brake .FYI

[Harvey Ziegler]

To check if your exhaust brake is operating you can go into the main electrical controls cabinet at the front of your coach..
The panel under the front driver side window. Find the relay that operates the exhaust brake solenoid. On mine it is relay K9.
Remove the wire that goes back to the exhaust brake solenoid. Wire number 204(exhaust brake solenoid on mine). Jumper
Positive to this wire and you should hear the brake solenoid operate. Note (you need to have air in your air tanks).
I usually do this each time that I lubricate the exhaust brake as it helps to work the lubricant into the bushings. 
Hope this helps you