Thoughts on rear air brake chamber assemblies

For the LMTV community (and should be similar for other wedge brake systems):

I had a noisy rear left side pair of air chambers after I shut down my M1081 LVAD. You could hear air leaking out of the spring chamber (larger inboard section that uses caging bolt). The air could be heard with or without the spring brake set or released, and only after the engine was no longer supplying air pressure, or if pressurized via the front emergency glad hand.

After lots of reading and some trepidation, I removed both assemblies from the truck. And here's my thoughts and some photos...
SAFETY FIRST! Those caged spring brake cans can be dangerous! The spring is the diameter of a regular car suspension spring and is highly compressed when properly caged.
1. I used the emergency glad hands to pressurize the brakes with the spring brakes released (knob pushed in), same could be done with engine air.
2. With the spring brakes released, I caged the spring brakes.
3. Apparently, pre-1998 LMTVs use smaller caging bolts due to a change in spring chamber size. NAPA TWD HD 10039 works)
4. Use a pen and put alignment marks and numbers on your air lines for both chambers, along with alignment marks for every fitting and along the length of each assembly, including the clamps. Must do, it's a pain to realign later...
5. Removal is pretty straightforward outlined in the TMs. You will have to get creative to loosen the locking nuts at the brake backing plate. You will need to remove all of the angle fittings from the front chamber to rotate it off the plate, and the inner and outer fittings from the rear chamber.
6. Removed all lines, including the CTIS line, and moved all of them inboard to be out of the way. Made it a lot easier.
7. The outer (smaller) diaphragm is glued to the shaft that pushes on the wedge. I peeled off the bad diaphragm and used acetone to remove the cement, and a wire brush to clean the surface. I used Goop Automotive to carefully glue the new diaphragms to the shaft, making sure it was centered properly. One chance on this.
8. Assemble the spring brake (inner) chamber first. I used a pair of screwdrivers to shift the spring-loaded center valve assembly toward the outer position and locked it there with another screwdriver across the face of the center assembly. This makes installing and centering the diaphragm much easier! When done fastening the spring diaphragm to the center section, carefully release tension on the center valve assembly.
9. Install the outer diaphragm with shaft, don't forget the nylon sleeve that's inside the shaft...
10. Make sure everything is properly aligned based on your pre-disassembly alignment marks. If you don't align everything, you won't get the assemblies to bolt up, especially the air lines.
11. Under the truck, I threaded the rear assembly on, bottomed the threads and turned it back out, but did not set the locknut yet.
12. I attached and tightened all of the T-fittings based on alignment marks, then the lines to the rear chamber assembly but not tightly, just got threaded nicely.
13. I then installed the front chamber assembly and right-angle fittings tightened properly to alignment marks. Again, did not lock the assembly to the backing plate.
14. I attached the lines from the rear assembly to front assembly.
15. By leaving both assemblies loose, I could rotate as necessary to get the lines aligned and threaded.
16. Now tighten all lines, then set the locknuts on the assemblies to the backing plate.
17. Pressurize your lines (engine or shop air via front emergency glad hand). Check for air leaks with spring brakes both pressurized and depressurized, check service brake, and shut off engine to listen for leaks. If your diaphragms are not centered and secured, you will get leaks. Fix them!

General note about rear chamber assemblies - there two major versions according to SuprMan, but I can identify three: Two "old" styles that use the smaller cage bolts and one "new" style using the larger bolts. The older can versions are only identified by disassembly of the spring chamber, but they both use the same internals. One has smooth lips for the diaphragm for both the can and the intermediate spring brake assemblies. The other has a raised outer ring on the intermediate section, which is used to center, retain, and seal the spring chamber diaphragm.
Turns out, the spring in the rear chamber had broken into two pieces and punctured the diaphragm, causing the leaking. With a replacement spring can assembly (finding out about the two variants of old can), I now have functional and non-leaking brakes.

Pics:
Center section of brake assembly. This is the inner, spring brake end pf the intermediate section. You can see the lip on one, no lip on the other. Flipped over looks the same but doesn't have a spring, and you pry from the other end to collapse this spring to make assembling the inner spring chamber and diaphragms much easier. Sorry, no photo, though I may mock it up later from leftover parts.
Several photos of the broken spring . Part of the spring had escaped from under the metal retainer that is grabbed by the caging bolt. Both spring halves got wrapped in each other, compounding the problem. Note size of the spring, hence the warning on proper procedures and safety. This got disassembled in the back yard, pointed in a safe direction, very carefully. Think loaded malfunctioned firearm...
Good (but muddy) photos of the air lines and alignment of parts (for those of you who take yours apart without marking them first!)

Pretty determined fellow there aren't ya. lol. How much money you think you saved in repairing your chamber? Most I've read say it is best just to replace the whole assembled chamber with a new one cause of the dangers involved in disassembly. Example.. yours had a broken spring.... what if that was not the case??? forces you would have been dealing with would be extensively more I'm guessing. Potentially very dangerous. Those springs can kill you.

My thoughts on taking a brake chamber a part is it's only a arms lengths from your face . I have repaired the type 30 chambers and when the spring is broken the tool won't go in straight and feels like it's pulling the spring with only one ear on the tool then I would take the clamp loose and hope it stays caged . Good write up and pictures I would replace the whole chamber .

Well, replacing the entire assembly would be much easier, but several things to consider:
1. Diaphragms are less than $5 each
2. Used assemblies mean used diaphragms. Are you willing to risk the time to put a used chamber in place and maybe have a leak that will still need repairing?
3. Prices for new assemblies, while not outrageous, is nowhere close to the price of just the diaphragms.
4. New Old Stock (NOS) parts are still Old parts and may have deteriorated rubbers.
5. I treat the spring chamber like a loaded weapon off safety. Point it in a safe direction. and treat with caution. I figure it's only going two directions - the spring one wau, the caging bolt the other, and act accordingly.
5. I'm a masochist when it comes to working on vehicles. I've got an LMTV (and really want a Tatra Kolos 813)

Working with that spring is no worse than disassembling a Macpherson strut and maybe safer as the spring should be contained in the can and go pretty much one direction only, caging bolt in the other.

And I've learned so much from this group, can't afford not to give back something. Bleeding-edge, so to speak.

One can buy new air cans for a reasonable price that's the way I would go my time is money. I would rather get right back on the road, and where I live any way I go I have to order in the parts and wait for them to arrive weather permitting.

Broke on the road makes sense to get the whole assembly. Sitting in the driveway not needed for work or anything, I had the time to order, take apart, reassemble, and learn. No pressure like being broken somewhere, thankfully.

Both directions on repairs are good thoughts I do myself usually buy a new part and get back on the road. However with that said, I still pull the old part apart to see what makes it tick. And then also repair it and have a spare to use or barter with. I have taken these apart and repaired them. really just a thick rubber disk and at 5 bucks why not. But after taking it apart I did look at the Caging bolt and laughed to myself at how small and feeble these jacking bolts seem to be at the tee. But they do hold and are probably stronger then they look. I was missing them from my truck when I purchased it, but I just bought new ones at my local shop. They were cheap and I have seen some used ones on other trucks and they look like they were worn pretty bad, like they had been used a few times. I'm sure they should last a long time minus if they were damaged in any way. But I really don't know. I guess I would treat them like a bolt, If its in good shape, not bent, and still has thread, then its ok! Correct me if there is a rule to go by for these Caging bolts.

acme66 did a detailed video in 2014 on replacing the diaphragms in a 5 ton spring-brake chamber.
[h=1]Replacing Spring Brake Diaphragms[/h]

Heh. Fix one thing, another breaks. Now that I've fixed the left side chambers, I now hear air from the right side chambers. I've already got two spare Type 9 diaphragms, just need to order the two Type 16 for the spring brakes. I'm getting a little too good at this...