New (Short) Style Airpack Rebuild Troubles

[silverstate55]

My truck's Airpack (new, short-style) had an issue several months ago with the air-slave cylinder, where it caused brake pressure to be applied while driving and the brakes were dragging. I removed the Airpack and rebuilt it with a kit from TNJ Murray. I took photos as I went along and I thought that I had everything reinstalled correctly; no instructions were included and I can't find any info anywhere on the rebuild procedures for the new-style Airpack...all the photos & instructions via MV Magazine are all related to the old-style Airpack.

Upon reinstallation, the truck wouldn't build air pressure at all. I sprayed soapy water everywhere with no luck. When shutting down the engine, I could hear a brief (3-5 seconds) of what sounded like air leaking down behind the dash cluster. I removed this and fired up the engine to try to build up air pressure to see where it might be coming from; no luck. I checked all these air fittings behind the dash, but nothing was kinked/leaking. Hmm.

I replaced the air governor (NAPA unit, $11); still no air pressure. I took the head of the air compressor apart & cleaned the gunk out of the valves, lubed up the O-ring on the unloader valve, and reinstalled everything. Still no air pressure. Finally I hooked up an air hose to the emergency gladhand and pressurized the air system, and air immediately poured out of the vent for the Airpack; the system wouldn't pressurize and all the air went immediately out of the Airpack vent line (the one that terminates above the engine air cleaner in the engine compartment).

I've searched for several days using various search terms throughout the Deuce & Deuce Mods sections without luck...a few posts came up where members had similar symptoms as I am having, but involved the old-style Airpack. I've looked through all of the TMs I could find online, but none show how to disassemble/service the newer-style short Airpack...I've even searched through the T-Pub site and a couple of other DOD sites, but no luck.

I can't find any instructions nor photos of the new style (short) Airpack being rebuilt...does anyone have any they can share? Did I install something wrong? The air pressure is going straight through the slave cylinder on the Airpack and out of the vent...it won't build pressure at all. What the heck did I do?

Thanks in advance for any help...maybe this will get some photos & instructions for the mysterious short Airpack finally posted.

 

[silverstate55]

Pulled the photos from my Blackberry (crappy camera, but better than nothing). These are of the short, newer-style Airpack I pulled from my Deuce before disassembly.




This unit had the newer-style air switch for brake lights, but the wiring was hooked up to the old hydraulic switch still in place. I removed the hydraulic switch and plugged the opening. The brake lights do work with the newer air switch.

 

[silverstate55]

I removed the air canister from the body; there was virtually no rust and the grease was still effective for the piston. No signs of tearing or dry-rot on anything here.

 

[silverstate55]

I removed the piston rod from the housing and disassembled it. The black cup on the left side of the piston rod was held in with a roll pin; I have roll pin removers but since I didn't see anything inside of it that looked like needed attention, I left it alone.





I tried to use these to orient myself on proper reassembly, but somewhere something went wrong...I have a feeling it's inside the air slave housing.

 

[silverstate55]

Here is the air slave housing as I disassembled it. I used everything from the TNJ Murray rebuild kit except for one O-ring; I couldn't find where it went. I replaced one item at a time, lubing O-rings & seals in silicone grease (NAPA Sil-Glyde, good stuff). No rust nor signs of corrosion were found on the piston nor anywhere in the air slave housing.





I thought I reassembled in the same order as I disassembled, and reconnected all the air lines in the same spots as before. I wonder if I simply reversed something inside the air slave housing that is causing air to bypass everything and exit via the vent line.

 

[welldigger]

I attempted a rebuild but mine was too destroyed to bother with. I did tear it completely down to study it. I ran into the same problem. There is almost zero data on the short style. Your problem sounds like something is hanging in the air slave housing. Pull that back off and see if it moves up and down freely. There is the piston with the large slot in the head that is in the air pak housing itself. This needs to also move up and down freely. If it won't pull out, remove the bleeder valve and push it out with a probe of some sort.

 

[m-35tom]

warren, i assume the blue piece will only go in one way? the small end of the gold part should go up against the small round rubber seal. this is just a air valve with a regulator built in, no brakes applied the pack is vented, brakes applied it closes the vent and regulates pressure depending on how hard you push the pedal.

 

[dburd72]

I just received the kit to rebuild my short air pack. If I can get some pictures of the dissemble I will post them to this thread.

 

[welldigger]

warren, i assume the blue piece will only go in one way? the small end of the gold part should go up against the small round rubber seal. this is just a air valve with a regulator built in, no brakes applied the pack is vented, brakes applied it closes the vent and regulates pressure depending on how hard you push the pedal.

That plunger is actually silver. It goes in one way and is held in place by a retainer clip if I remember correctly.

 

[silverstate55]

AH-HA! I FOUND OUT THE PROBLEM!

I reversed the installation order of the air slave housing components. When I disassembled this one, like a dummy I was holding the housing too vertical to get the blue-anodized air slave piston out of the housing (held in with O-ring friction); when it came out, the top spring & 4-prong flat cap fell out, and I didn't get to see the order in which they should have been installed. I made my best guess (I should take notes & highlight the areas where guesswork is involved, 99% of the time this is where I make my errors...) and installed the 4-prong cap first then the spring, and the blue-anodized air slave piston didn't want to go in very easily.

The correct order of installation into the air slave housing should be: small top spring | 4-prong flat cap | blue-anodized air slave piston | snap ring | larger spring | gold-anodized lower pressure piston. So in the second photo, the order of the two items on the right should be reversed...when installed as I have it laid out in the second photo, air pressure will pass directly through the Airpack and exit via the vent in the engine compartment by the air cleaner.

I'll do a disassembly/reassembly how-to write-up with photos in another thread to make it easier for those who have mastered the Search function.

I spent all day yesterday working on this, and then re-installing it and bleeding the entire brake system. My truck built up immediate air pressure, and once the Airpack & brakes were bled, you just have to barely press the brake pedal to get a quick stop.

Thanks to all who have offered help! I appreciate it!

 

[silverstate55]

I did notice on the 2 trucks I have with this new-style Airpack, the air lines as they exist in stock form are almost impossible to get crossed up...of the 2 air lines with similar-size fittings, one is a fine-threaded compression fitting and the other is a coarse-thread flared fitting. The other is a larger fine-threaded compression fitting. It would be very difficult to swap these lines, but I'm sure that somewhere there's someone who tried.

 

[wildbill88]

I did the rebuild on mine and still the brakes still hang up and I think the relay valve is to blame I bought the old style air pack but I still want to get my shorty working did you ever do the write up on this ??

 

[silverstate55]

I did the rebuild on mine and still the brakes still hang up and I think the relay valve is to blame I bought the old style air pack but I still want to get my shorty working did you ever do the write up on this ??

http://www.steelsoldiers.com/showth...hort)-Airpack-Teardown-amp-Repair-with-Photos