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Old 06-03-2021, 03:46 PM   #1
Epp
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Exhaust Brake Info/Help

Hello all,
We recently purchased a 2001 Newmar dutchstar DP with the Cummins ISC engine on a Spartan chassis.

We upgraded from a 1999 Newmark dutchstar DP, Spartan, Cummins ISC.

In driving this new rig, the exhaust brake does not seem to be working like Iím used to.

On the old rig when you would engage the exhaust brake and take your foot off the throttle it would downshift immediately to I believe 4 on the transmission keypad and you could feel/hear the exhaust brake engaging in the back.

On the new rig when youíre driving and engage the exhaust brake, the transmission shifts down to 2 On the transmission keypad and you do not hear or feel the exhaust brake engaging.

It is at the Cummins dealer right now doing some other work to the engine and I had them mechanically check out the exhaust brake actuator and butterfly valve and they report back everything mechanically is good.
They suggested I would need to start troubleshooting at the switch or fuse. It seems like the transmission keypad is getting the signal the exhaust brake is on, so I would assume the switch is good but would there be a separate fuse going back to the actuator in the engine compartment? Did Spartan change out how the exhaust brake works between 99 and 2001? Any input or education would be greatly appreciated.

Thanks,
Thescoutranch
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Old 06-03-2021, 04:17 PM   #2
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In my '02 rig with the Allison and exhaust brake, it's speed dependent. The display might say '2' but the brake is either really gentle or not engaging above a certain speed. I've gotten used to it and just apply brake for a couple seconds to drop speed then it engages. At traffic speeds, 35 MPH or so, it definitely engages strong.
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Old 06-03-2021, 04:30 PM   #3
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Quote:
Originally Posted by Epp View Post
Hello all,
We recently purchased a 2001 Newmar dutchstar DP with the Cummins ISC engine on a Spartan chassis.

We upgraded from a 1999 Newmark dutchstar DP, Spartan, Cummins ISC.

In driving this new rig, the exhaust brake does not seem to be working like Iím used to.

On the old rig when you would engage the exhaust brake and take your foot off the throttle it would downshift immediately to I believe 4 on the transmission keypad and you could feel/hear the exhaust brake engaging in the back.

On the new rig when youíre driving and engage the exhaust brake, the transmission shifts down to 2 On the transmission keypad and you do not hear or feel the exhaust brake engaging.

It is at the Cummins dealer right now doing some other work to the engine and I had them mechanically check out the exhaust brake actuator and butterfly valve and they report back everything mechanically is good.
They suggested I would need to start troubleshooting at the switch or fuse. It seems like the transmission keypad is getting the signal the exhaust brake is on, so I would assume the switch is good but would there be a separate fuse going back to the actuator in the engine compartment? Did Spartan change out how the exhaust brake works between 99 and 2001? Any input or education would be greatly appreciated.

Thanks,
Thescoutranch
I think you really need to diagnose this on your own. Can you pull up a rear hatch and actually "see" the pacbrake? If so, have a helper sit back there with a flashlight and watch to see if the pacbrake is actually functioning (valve opening or closing) while you are driving. You'll need to get up to speed for it to work. If the pacbrake isn't functioning when you press on the switch/button, then you you could run a 12v jumper wire to one of the terminals on the activation switch near the pacbrake and see if it comes on. Maybe that switch is bad or a loose connector. My brake was stuck wide open and would never close. I found this out on a 10% grade:-( I did the same test with my son in the back. Also, Pacbrake has upgraded their product for your coach so in the event yours needs replacing, you will be getting the newest version.
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Old 06-03-2021, 05:52 PM   #4
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Quote:
Originally Posted by Mile Marker 42 View Post
I think you really need to diagnose this on your own. Can you pull up a rear hatch and actually "see" the pacbrake? If so, have a helper sit back there with a flashlight and watch to see if the pacbrake is actually functioning (valve opening or closing) while you are driving. You'll need to get up to speed for it to work. If the pacbrake isn't functioning when you press on the switch/button, then you you could run a 12v jumper wire to one of the terminals on the activation switch near the pacbrake and see if it comes on. Maybe that switch is bad or a loose connector. My brake was stuck wide open and would never close. I found this out on a 10% grade:-( I did the same test with my son in the back. Also, Pacbrake has upgraded their product for your coach so in the event yours needs replacing, you will be getting the newest version.
I found when dealing with my 2005 Monaco Diplomat that a simple and quick way to really see if there is an issue is to do the above. I actually secured a GoPro on the engine cover edge and drove the coach. The problem, you can't cause the system to work, unless you're driving the coach. You can use a 12 volt jumper to actuate the piston, but it doesn't tell you if it's getting power while driving.
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Old 06-03-2021, 06:36 PM   #5
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My coach also has the 2001 ISC. The way to test exhaust brake is, find a deserted stretch of road preferably with a hill. Manually put trans. in 2nd gear rev it up good and let off, get the feel for how it decelerates, then start turning exhaust brake on and off and you can feel it and know the difference between how trans feels and exhaust brake!
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Old 06-04-2021, 03:21 AM   #6
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Quote:
Originally Posted by Epp View Post
Hello all,
We recently purchased a 2001 Newmar dutchstar DP with the Cummins ISC engine on a Spartan chassis.

We upgraded from a 1999 Newmark dutchstar DP, Spartan, Cummins ISC.

In driving this new rig, the exhaust brake does not seem to be working like Iím used to.

On the old rig when you would engage the exhaust brake and take your foot off the throttle it would downshift immediately to I believe 4 on the transmission keypad and you could feel/hear the exhaust brake engaging in the back.

On the new rig when youíre driving and engage the exhaust brake, the transmission shifts down to 2 On the transmission keypad and you do not hear or feel the exhaust brake engaging.

It is at the Cummins dealer right now doing some other work to the engine and I had them mechanically check out the exhaust brake actuator and butterfly valve and they report back everything mechanically is good.
They suggested I would need to start troubleshooting at the switch or fuse. It seems like the transmission keypad is getting the signal the exhaust brake is on, so I would assume the switch is good but would there be a separate fuse going back to the actuator in the engine compartment? Did Spartan change out how the exhaust brake works between 99 and 2001? Any input or education would be greatly appreciated.

Thanks,
Thescoutranch
I agree with you.
Pacbrake operation is:
1) Switch on
2) Speed above 10 mph
3) Lift foot from accelerator pedal - throttle position is sensed at 0
4) TCM/VIM send signal to air solenoid and trans
5) Trans tries to shift to either 4th or 2nd and Pacbrake cylinder activates.

As mentioned, open engine hatch in BR and have someone watch the cylinder to see if it is activating. With the hatch open you should be able to hear the air solenoid working. My pacbrake butterfly was frozen and the end of the pacbrake cylinder had broken off. The pacbrake mechanism needs to be lubed on a regular basis.
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Old 06-05-2021, 07:25 AM   #7
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In some of the readings I’ve done on here it sounds like you can have the ECM/transmission reprogram to a specific gear for when the exhaust brake is activated. I guess that would depend on what areas you’re planning to be driving in, or live in. My last one was programmed for forth gear, this current one is programmed for second gear.

Side question: any inputs on whether I should have it reprogrammed to third or fourth gear instead of second for the exhaust brake operation? Primarily we will be traveling throughout the southern United States.

It sounds like the signal from the switch does go through the ECM to control the operations of the exhaust brake and transmission gear selection.

In reading here , it sounds like the ECM uses both a speed signal input and the throttle position input to enable the operations of the downshifting in the engagement of the exhaust brake. The fact that my transmission selector indicator shows that it is downshifting to second gear when the switch is on leads me to believe that both the speed sensor input in the throttle position input is reaching the ECM in the ECM is out putting the signals to enable the exhaust brake.
Are these assumptions correct?

If so, this leads me to the belief it may be a separate fuse controlling the 12 V feedback to the actuator, or a break in the wire supplying the 12 V back to the actuator?

Trying to find a volunteer to ride in the bedroom with the engine compartment open to test this is going to be tricky, LOL.

I like the idea of the camera, I do have a Garman dash cam that I may be able to relocate for this test.

Right now the rig is down a Cummins San Antonio getting a whole mess of oil leaks repaired that I inherited from the previous owner.
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Old 06-05-2021, 11:18 AM   #8
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I believe that the shift to 2nd gear is how they come from the factory. Some like to change it to 4th, as the don't like it coming on in the lower gears.

I bought a new 2005 Monaco Diplomat and the transmission would shift, but the exhaust brake would not come on. After several tries at an authorized shop, to get it fixed, I gave up and just wired a switch to the unit with 12 volts. It actually worked out well, it gave me a two speed exhaust brake, one that downshifted and one that let me just turn on the exhaust brake.

Lastly, if the exhaust brake is working, it snaps the flap open pretty hard and fast. You could take some soldering wire and attach it to the arm/mechanism and see if it breaks the wire.
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Old 06-05-2021, 11:36 AM   #9
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Yup, as already posted verifying exhaust brake function is very easy.


On an open stretch of road, select a gear 3 or 4 work well. Accelerate to the upper end of the engine's RPM range.


Let off the throttle and coast. Do it again and engage the exhaust brake.


And, you can toggle the exhaust brake on/off/on and should feel the difference, particularly at higher engine RPM.


Note, if PacBrake, they DO require routine lubing or the brake can seize:


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


The second picture on that page shows where to oil it.


If not lubed, particularly if the coach sits for long periods of time and even worse, if the engine is started but not driven enough to fully warm up, a seized brake butterfly as quite common.



And, if the exhaust brake is seized, suggest you consider upgrading to the PacBrake PRXB model. Stronger braking HP at lower RPM.
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Old 06-14-2021, 12:10 PM   #10
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I have not had a chance to do the driving test to check out the exhaust break yet. What I was wondering was, in the driveway, if I start the rig and let it idle I assume I could go back to the exhaust brake relay that’s located in the back electrical compartment and jump pin 30 over to 87 which should activate the exhaust brake and I should be able to hear the exhaust brake engage since it should be loud correct? Is there any issue with engaging the exhaust brake seating at idle RPM in park?
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Old 06-14-2021, 12:13 PM   #11
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Better:


Air pressure built until governor cuts out/full air pressure.


Engine OFF.


Disconnect the positive connection to the exhaust brake solenoid (engine compartment).


Jumper 12VDC positive to it.


Should slam shut with authority and when jumper is removed snap open with authority.


If a PacBrake, be sure to lube it:https://pacbrake.com/product/c18037-superlube/
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Old 06-14-2021, 09:16 PM   #12
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I will give that a try. Thanks
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