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Old 05-06-2021, 06:28 AM   #1
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Exhaust brake

1995 American Eagle, 8.3 Cummins , Pac brake ,exhaust brake stops working after engine get to operating temp or after you drive coach a few miles any one ever hat this problem ? Thankd
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Old 05-06-2021, 06:43 AM   #2
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Quote:
Originally Posted by bigslim View Post
1995 American Eagle, 8.3 Cummins , Pac brake ,exhaust brake stops working after engine get to operating temp or after you drive coach a few miles any one ever hat this problem ? Thankd

You can TRY to free it up (remove it and use penetrating oil).


Thereafter, you can lube it per PacBrake's instructions:

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


If it won't free up, upgrade to a new PacBrake PRXB brake. More braking HP at lower RPM.


My concern is if it is seizing up, it COULD seize in the fully closed position which would mean NO POWER and extreme exhaust temperatures (have seen exhaust manifolds glowing red hot when this happened).
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Old 05-06-2021, 08:44 AM   #3
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Yes, I had/have this problem. Mine works when it wants to. I think my problem is throttle position sensing.
As wolfe mentioned, make sure you use the correct lube and keep it lubed.

Do you know if it even activates the cylinder at all?
Operation rules for my Pacbrake system are:
1) On/Off switch on dash On. This applies 12V to system.
2) Move faster than 10mph. This is the minimum speed.
3) Lift foot from pedal and this sends signal to air solenoid to activate cylinder.
4) Tranny tries to downshift to preprogrammed gear, dependent on speed/rpm. Tranny won't hurt itself.

You should lift the bed and lift the access panel to the engine. Have someone stand/squat back there with a flashlight and watch the cylinder as you get the speed above 10 mph. Then remove foot from pedal. I can hear the air solenoid activate when I do this.

I added a foot pedal that applies a ground where the TCM usually applies it (I cut into line, inserted a SPDT switch and added the foot switch/ground to one side of SPDT. I can press the foot pedal even if sitting still and it would activate the air solenoid, if the On/Off sw on dash was on. This does two things - allows me to check if it's working and also to over-ride it if it isn't.
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Old 05-07-2021, 04:02 AM   #4
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Quote:
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I added a foot pedal that applies a ground where the TCM usually applies it (I cut into line, inserted a SPDT switch and added the foot switch/ground to one side of SPDT. I can press the foot pedal even if sitting still and it would activate the air solenoid, if the On/Off sw on dash was on. This does two things - allows me to check if it's working and also to over-ride it if it isn't.
Do you have any details/pics on this mod?
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Old 05-07-2021, 03:23 PM   #5
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Do you have any details/pics on this mod?
I've attached the foldout J-1 schematic from WTECII troubleshooting manual. If you don't have this manual let me know. The connections on the left are on the bottom of the shifter - there are two connectors.

When the switch on dash is on, you're traveling above 10mph and you lift your foot off the pedal the ECU/TCM applies a ground on pin A32 (wire 132) to pinB1/M1 on VIM to activate the relay that controls the air solenoid that controls the PacBrake cylinder.
I also attached another doc that more easily shows pin D2 on VIM sending the control signal to air solenoid.

What I did was cut wire 132, insert a SPDT switch - one pole "Auto" the other "Manual", the common pole goes to B1. When in "Auto" the normal signal comes through to B1. In "Manual" the Foot Switch passes a ground when depressed, to B1. The foot switch is a simple SPST switch in a foot activated pedal. I can't remember where I bought it - probably Amazon.
If you need more clarification let me know.
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Old 05-08-2021, 05:16 AM   #6
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I've attached the foldout J-1 schematic from WTECII troubleshooting manual. If you don't have this manual let me know.
Thanks for the info. No, I don't have a copy of this manual. I've sent you a PM with my email address. If you could send me a copy, I would appreciate it. Thanks again.
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Old 05-09-2021, 06:27 AM   #7
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Here's a link to the recommended maintenance of the Pac Brake.
https://pacbrake.com/wp-content/uploads/L6111.pdf
They recommend using a High Temp lube on it, I bought a bottle and it goes a long ways. https://pacbrake.com/product/c18037-superlube/ You can buy it on line.


I actually lubed mine this week. I actually completely removed the cylinder so I could work the butterfly valve.
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Old 05-09-2021, 10:48 AM   #8
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I also have a MM Spartan where are these wire located. Near the accelerator pedal
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Old 05-09-2021, 04:28 PM   #9
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I also have a MM Spartan where are these wire located. Near the accelerator pedal
I am not sure who you are asking. If you are asking me, the wires come out of the bottom of the shifter assy. Nice thing about Spartan is that each wire is numbered on the wire and the color is correct also.
If you're not asking me, I'll go back to sleep
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Old 05-09-2021, 04:30 PM   #10
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Originally Posted by jacwjames View Post
Here's a link to the recommended maintenance of the Pac Brake.
https://pacbrake.com/wp-content/uploads/L6111.pdf
They recommend using a High Temp lube on it, I bought a bottle and it goes a long ways. https://pacbrake.com/product/c18037-superlube/ You can buy it on line.


I actually lubed mine this week. I actually completely removed the cylinder so I could work the butterfly valve.
I should do that also. That way you KNOW the butterfly is free. On the to-do list.
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Old 05-24-2021, 02:47 PM   #11
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Sorry to take so long to respond. ive located the wire harness and wire #132 if i understand this correctly all I need to do is ground out # 132 to make the exhaust brake work. I have let my grandson drive and I watched the exhaust brake and it doe not always close. When the brake is working properly the shift panel display always drops to 2 gear when its not working it stays on 6 gear. Cliff bigslim43@yahoo.com
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Old 05-24-2021, 02:51 PM   #12
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When the brake is working properly the shift panel display always drops to 2 gear when its not working it stays on 6 gear.

Then, there is an electrical issue up front.


First "suspect": the throttle does not "read" as closed. And, if the Allison ECU does not see the throttle closed signal, it will not activate the exhaust brake.
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Old 05-26-2021, 04:51 AM   #13
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I would agree with Brett. For my system I have a physical throttle cable that runs from the foot pedal back to the engine. We have not been able to locate where the throttle position switch is on the engine end. On an Electronic throttle the sensor is usually on the foot pedal.
After talking to John at Transmission instruments I think maybe I have an intermittent +12V at the on switch. I am going to wire in an LED that will show +12V when the switch is on. If I see it turn on and off, then I'll know.

Cliff, I inserted a switch on wire 132 to switch the input to the Vehicle Interface Module (VIM), from the TCM to the foot pedal. The TCM applies a ground to 132 to activate the relay in the VIM shown on the schematic, automatically. My foot pedal applies a ground to the VIM input if I have the switch I added to 132 in the foot pedal position, and I press the foot pedal.
The relay applies whatever voltage is on D2/E2 to the air solenoid that activates the Pac Brake cylinder.
So Cliff, I would not just ground out wire 132 while it is still connected to the TCM. You want to apply the ground to the VIM input. I cut the 132 wire and crimped on bullet connectors so I could re-connect wire 132 if needed. Then I inserted the SPDT switch so I could select the signal I wanted to apply - the original signal that is automatic from the TCM or the manual signal from the foot pedal.
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