PAC Brake air leak

[Open Roaders]

We have a major air leak on the air in side of the pac brake. When the brake is activated full air pressure is blowing out of the point indicated in the photo.

I’ve researched but I can’t find any pictures showing a PAC Brake with a ‘T’ piece at this point only a 90 degree connector for the air line in.

Should there be a plug in here that has worked it’s way loose? There is a thread in there.

Thanks for any help.

Cummins 8.3 mechanical engine

[Bigd9]

I can't tell from the picture, but let me say PacBrake did use a dual acting pneumatic cylinder for some uses. Could there be another airline that is loose around there? Maybe it goes into the hole you are referring to? does it look like the cylinder with the two red cps in this link?
https://pacbrake.com/product/exhaust...tic-actuators/

[Open Roaders]

Originally Posted by Bigd9

I can't tell from the picture, but let me say PacBrake did use a dual acting pneumatic cylinder for some uses. Could there be another airline that is loose around there? Maybe it goes into the hole you are referring to? does it look like the cylinder with the two red cps in this link?

https://pacbrake.com/product/exhaust...tic-actuators/

I haven’t seen any lose hose that may have fallen out but I’ll take another look. Nothing else seems to be failing that might require air. Thanks

[Open Roaders]

I’ve finally found a picture online of another one similar.
There is a plug!
I just don’t want to plug something that should be breathing!

[twinboat]

Could have had a release valve in that spot.

If you plug it, make sure the cylinder operates quickly.

[Bigd9]

I'm being cautious since your coach is a tad more mature than mine, but I would plug that hole. The PacBrake on my 2006/Cat engine only has one air line(air hose) going to it. Here is a picture of mine

[Bruce Anthon]

Originally Posted by Open Roaders

Attachment 387094

I’ve finally found a picture online of another one similar.
There is a plug!
I just don’t want to plug something that should be breathing!

I do not have a PAC brake on my coach but looking at your pictures I have a couple of comments. I think what you see here in this photo is a square 90 degree fitting, not a T with a plug. The elbow fittings are available with a square head or hexed. The suggestion to plug it and test is the way to go.

In the picture you sent with the arrow and the note air blowing, it looks like the pivot pin and bushing under the “C” clip have a lot of play. You might want to see if it is supposed to be that way or just showing a lot of wear. Since you are there it should be easy to address if needed. Be sure to lube it at the same time.

[jacwjames]

I'd suggest calling PacBrake
https://pacbrake.com/contact-pacbrake/




Not sure but there has to be a way for air to release after you shut off the PacBrake.

Do you know if the air leaks while the PacBrake is being used, only way to tell would be to have someone observe.

[Skip426]

Originally Posted by Bigd9

I'm being cautious since your coach is a tad more mature than mine, but I would plug that hole. The PacBrake on my 2006/Cat engine only has one air line(air hose) going to it. Here is a picture of mine

You'll have to follow the air supply line back to the frame ; I believe you'll find a combination air solenoid supply/vent , that dumps the air from the activation cylinder when the exhaust brake is not in use , allowing the cylinder's internal spring to disengage the brake.

[Open Roaders]

Originally Posted by Bruce Anthon

I do not have a PAC brake on my coach but looking at your pictures I have a couple of comments. I think what you see here in this photo is a square 90 degree fitting, not a T with a plug. The elbow fittings are available with a square head or hexed. The suggestion to plug it and test is the way to go.

In the picture you sent with the arrow and the note air blowing, it looks like the pivot pin and bushing under the “C” clip have a lot of play. You might want to see if it is supposed to be that way or just showing a lot of wear. Since you are there it should be easy to address if needed. Be sure to lube it at the same time.

Thanks, I’ll check out the wear at that point.

[Open Roaders]

Thanks all, Plug & test is our plan. Of course we discovered this on a Saturday afternoon. I’m intending to give Pacbrake a call on Monday.
I don’t believe they provide the fittings for the airline just the orifice to connect into so it would be the engine manufacturer or coach builder who fitted it.
I’d be interested to know what that take off point was for, if anything.
I’ll let you know what I find.

[Bigd9]

I had the PacBrake worked on by 4 different Cummins shops while our previous 1997 coach was under warranty. Each time they would swear they "put eyes" on it while they drove it and it was working. They all lied to me.

When I got home from the last shop, I looked at the PacBrake and found they had not only disconnected the air line, but plugged both the air line and the cylinder with several brass fittings. The air line was hanging down with the weight of all the brass fittings!

I gave up on Cummins and carefully searched for the problem and finally found it When the engine was fitted with the exhaust brake, someone forgot to plug it into the engine wiring harness!! All I had to do was remove the protective plastic plug cap and plug it in and it worked.

All this to say, someone in the past could have added or changed that fitting. Maybe they were putting a pressure gauge on that port you have to see if air was getting to the cylinder. Who knows.

Good luck and I hope you get to fix the problem. BTW, how did you find out air was blowing out of that fitting?

[Open Roaders]

Originally Posted by Bigd9

: BTW, how did you find out air was blowing out of that fitting?

I can hear the normal hiss when the pacbrake engages when the foot comes off the accelerator. This time the noise was not normal and was much louder.
We checked it at our destination and with the engine not running engaged the pacbrake and watched air under full pressure gush out of the fitting.
I’m in contact with pacbrake now via email but I’m not sure their reply is accurate. I’m going to try to speak to someone. We’re currently in Mexico

[Ray,IN]

Apparently that Tee is also a quick release valve that dissipates air pressure too.
reference item 2,of L1015pdf https://support.pacbrake.com/wp-cont...oads/L1015.pdf
I suspect if that hole is plugged the brake cannot release quickly.

When a PacBrake is operating correctly, it should disengage at about 800 RPM.


You can download the installation manual for your engines air actuator from: https://support.pacbrake.com/service-support/
FWIW, a modification does show 2 air lines to the actuator.