M220 AirPak rebuild.

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USMC 00-08

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Am I understanding right that all we need out of the 5 ton airpak is this??? I pulled this out of an 800 series airpak.
100_2428.jpg100_2429.jpg100_2430.jpg

That will allow us to use the 5 ton rebuild kit? Will all the seals we need be in that kit?
 

m1010plowboy

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G749 Airpak - GG Piston measurements

Here's GG - Piston 7410852 out of a G-749 Air-Pack-Kit

air pak 15 008.jpgair pak 15 009.jpgair pak 15 010.jpgair pak 15 007.jpgair pak 15 006.jpgair pak 15 005.jpg

It looks different but the pictures don't mean anything until we get the tree calipers out.

For additional AIR PACK information here is the info out of the ORD 7 SNL G749 for the AIR PACK.
It includes a little statement on the right hand side of the page,

UNIT, air power, assy (issue until stock is depleted), then use UNIT, 2530-318-0997-G749

I have no idea if this is an optional FSN or NSN # to find alternative parts so maybe someone more familiar with the jargon can help explain. I'm not having any luck chasing down that number.

This kit came out of Tower Park in 2013.

airpak nsn 001.jpgairpak nsn 002.jpg

Is it time to call the Bendix kids again?
 

USMC 00-08

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I got some clarification from Oldfart last night.

These pics are of the G749(left) and M54/M800(right) pistons next to each other. The M54 piston internals are a larger diameter but the externals are the same diameter.
Power pistons.jpgPower piston internals.jpg

Here is what Oldfart told me:

"It is my understanding from Gun Freak that he found some original seals after some extensive calling around to Bendix people. We were not so lucky. The 5 ton airpak rebuild kit has a few “extra” gaskets, but everything in the kit will fit the GMC 2.5 ton airpak except the power piston seals. The 5 ton power piston is different in piston diameter, but the assembly itself has the same outer diameter and threads in place of the 2.5 ton piston assembly. Our experience was a slight softening of the breaking rate. I with the original piston, it was almost impossible to not lock up every wheel on the truck. While it is still very easy to lock up the wheels, one can actually feather the brakes and keep from putting passengers on the windshield."
 

m1010plowboy

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Air-pak dismantled

A couple of northern, fabricating, tin bashing, mechanically inclined young bucks that don't mind sharing their success couldn't get that big piece to un-thread from its perch.....so they made a tool.

It's a socket with wings which could help someone down the road.


P4121793.jpgP4121786.jpgP4121785.jpg
 

m1010plowboy

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I'm just the guitar player on the fence but I will follow up with the tool. I could schpeculate that it's just a socket but I'll ask the boys.

These pictures just showed up on my phone. The new G749 team are taking pictures so I'll grab some once the 'get er done' panic is over.


airpak 002.jpgairpak 003.jpg
 

USMC 00-08

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What oil are you going to use in the airpak? Some people suggest hydraulic jack oil and some say air tool oil.

I ended up using the hydraulic jack oil,l but would like to see what your thoughts were.
 

m1010plowboy

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What oil are you going to use in the airpak? Some people suggest hydraulic jack oil and some say air tool oil.

I ended up using the hydraulic jack oil,l but would like to see what your thoughts were.
This would be an opportunity for someone with a ton of air-pak experience to jump in and give us some feedback. It's only a big deal if what we add melts rubber and gums up the seals.....like the time I put motor oil into a chevy brake reservoir. lol.

I think the book says OHT but nailing down what that cross-references to should be documented. Air-tool oil is on the shelf so before its used, maybe the air-pak wizard will chime in.
 

SturmTyger380

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You need oil that is friendly with rubber and as I understand the air tool oil fits that bill. You don't need a ton of it. Maint manual called for removing the square headed plug on the back of the airpack and giving a squirt or two.
 

tlmob1

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I must have missed out on where you picked up the M54/800 airpack rebuild kit. Just in case I need to get one. any assistance would be appreciated.
 

Oldfart

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I must have missed out on where you picked up the M54/800 airpack rebuild kit. Just in case I need to get one. any assistance would be appreciated.
We got ours off eBay. Can't remember the exact price we paid, but it was not much. Sticks in my mind it as around $10.
 

Brad

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As I have posted on here numerous times, we have had a continuing problem with the brakes on my Dad's M135 contually locking up.
I have re-done eveything, and paid to have the airpack rebuilt by a supposed expert, twice.
Still am about ready to give up. Almost.
Would you consider rebuilding ours. We would of course pay whatever the fair cost?
Just considering??
The truck, nice as it is is worthless if we cant drive it.
RegardsTrk 7.jpgTRK2.jpg
 

Oldfart

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As I have posted on here numerous times, we have had a continuing problem with the brakes on my Dad's M135 contually locking up.
I have re-done eveything, and paid to have the airpack rebuilt by a supposed expert, twice.
Still am about ready to give up. Almost.
Would you consider rebuilding ours. We would of course pay whatever the fair cost?
Just considering??
The truck, nice as it is is worthless if we cant drive it.
RegardsView attachment 652537View attachment 652538
I am wondering what you mean by "lock up". We have someone in our club with an upgraded Deuce where the brakes were converted to a dual master cylinder. After a couple of stops, his brakes lock up and he can't get them to release unless he bleeds off a brake line. If by lock up you mean the brakes are very sensitive and grabby, we find that is common to many M211/M135 series including our M220.
 

m1010plowboy

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We should keep the JollyRoger rebuild sticky as a learning thread and put your solutions on one of your original threads Brad. It's all good information that we like to keep for future "Brake Problems", so we'll link your solutions over here http://www.steelsoldiers.com/showthread.php?159330-never-ending-M135-brake-problems!!-Need-advice so we can find you.

The Air-Pak challenge might be solved with a simple cleaning and lubrication of the large diameter "Air" side of the Air Pak but there is a way to determine if it's a hydraulic or air problem. Draining the air-tanks each time you drive it may help keep this from happening.

PA310094.jpgPB010141.jpg

We were fortunate enough to have 2 trucks go through the "Brakes lock and don't unlock when pedal pressure is released" symptom. We started to do forensic work on the Air-Paks to see if we could nail down the problem.

There is one easy step to see if the large piston is coming all the way back which allows fluid to flow 'away' from the wheel cylinders. 3 steps if you haven't already opened the valves on the air-tanks.

1) Open valves on air-tanks to be sure there is no air pressure in the system.
2) Remove small plug at back of air-pak.
3) Insert measuring device into hole and see what your dip depth is.

The depth on a fully seated air piston is 1 1/4"

PB030158.jpgPB030162.jpg

If the large piston is properly seated then it is possible the valve that allows 'brake fluid' to return through the air-pak is hung up, sticking, not moving properly.

This next step needs to be done once the brakes are properly set up which means jacking up the truck and following more simple steps listed on page 439 of the 9-8024 TM.

Once the brakes are set properly you just open the valves on the air-tanks and test for proper operation of the brakes without air assist. The way this landscaper is reading things, the fluid flows into "G" inlet line and out through "H" the outlet line as long as the rod "MM" is in the fully returned position. If the brakes return properly without air, then the problem is in your "Air" side of the system, which can be an easy fix.

PB010139.jpgPB010138.jpg

If the fluid does not return properly and release brakes, then the problem is likely with piston "GG" which is more difficult to get at or "A" which sits at the start of the air supply line. .

PB010134.jpg

Get the brakes set back up properly, test the beast without air and dip the air side, large piston to see what you're dealing with before you do another tear-out.

There could also be a slight deflection/ dent/ deviation in the shape of the large canister which will hang up the large piston and prevent it from returning to the 'full open' position. This Plate/Packing assembly (H&G), shows a slight oval in the housing which could be a part of our problem on Gizmo, the M135. Gizmo's owner suggested using a pipe with the same outside diameter OD as the inside diameter ID of the canister to help round things out.

PB030164.jpg

If the problem is just with the air side of the Air-Pak then it's only the air pipe and the large canister that need to come off for cleaning. We still need to be careful with dismantling the large canister. I'm tearing down 2 air-paks and on one of them the canister to housing rubber seal appeared soft and stretched out when I pulled the canister off. We need to check if one of the 'newer style' air-pak kits has this seal or find an alternative.

PA310127.jpg
 

USMC 00-08

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That last seal you mentioned is in the rebuild kit I got. What I don't know and should have checked, is if it is a standard o-ring size that you can get anywhere, without having to buy the whole kit to get it.

I also used the power piston out of an M809 series airpac like is mentioned in this rebuild thread.
 
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