FMTV brake canister diaphragm replacement.

[GeneralDisorder]

I've seen a few questions posted about replacement canisters - which are a bit difficult to find and expensive on the surplus side. I recently replaced the diaphragm's in all of mine and other than dealing with the paint on the clamp bolt threads it's an extremely easy process. On my 2008 A1R the front brake cans use a "Type 16" diaphragm, and the four rear cans all use a "Type 12" diaphragm. The diaphragms were about $6 each for the rear, and about $8 each for the front. The whole job took about an hour.

The process is very easy - DON'T TOUCH THE OUTER CLAMPS on the rear cans. That's the parking brake spring and IT CAN KILL YOU.

The front is easy - take the clamp off, remove the diaphragm, replace with a new one, and reinstall the cap and the clamp.

On the rear - you have a choice to make. On a flat level surface you can chock the wheels and release the parking brake with air, then take the INNER (CLOSEST TO THE WHEEL) clamp off, replace the diaphragm, and reinstall. Or if you aren't on a real level surface or want to be extra safe you can cage both of the canisters on one side while the other side parking brake remains engaged.

5 of mine (LMTV) were not that bad, but one of my rear diaphragm's was not looking excellent:

 

[aw113sgte]

This is the reason I support this forum. Awesome info, have been planning to do this.
How did you determine the sizes for those who don't have a similar year?

 

[GeneralDisorder]

Got into the TM and cross-referenced the NSN's over to the Meritor part numbers and took those to a local brake shop - turns out the Meritor part numbers for the front end in "-16" and the rear "-12" which the guy immediately recognized as type 12 and type 16. Type 12 is a 5.5" diaphragm with a 1.75" travel, and type 16 is a 6" diaphragm with 1.75" travel. They are standard and stocked at every air brake and heavy duty shop. Haldex part numbers DP12 and DP16.

You can just pull one out and measure it with a tape measure if you aren't sure. Like I said it's REALLY easy. Barring rust of course.

 

[aw113sgte]

If feeling frisky, park brake diaphragm replacement:

 

[chucky]

 

[GeneralDisorder]

Yeah I'll likely do the parking brake diaphragms at some point also. If you have a failure on one of those it's easy enough to cage it, plug the air line and drive on with three. Losing the service brake diaphragms however can be a real significant problem for "getting home" - uneven brake application with a wheel disabled can cause brake steer...... I got an extra of each diaphragm to keep in the emergency parts box for the road. Probably the cheapest part I've found yet on these trucks that wasn't an off-the-shelf fastener or a Shrader core or something.

 

[Keith Knight]

How did you identify which one was giving you problems before you took it apart?

 

[GeneralDisorder]

How did you identify which one was giving you problems before you took it apart?

Wasn't experiencing problems. This was an effort to avoid future problems. Rubber deteriorates, can't see the condition without opening them up and being 15 years old...... the price doesn't justify inspection even. Mileage is meaningless on a truck that sat in the desert all it's life so they just needed to be changed in my opinion. And it would appear that at least in the case of that one pictured it was a decent investment.

 

[Keith Knight]

Well that sucks, my 2003 A1 rear brake chamber diaphragms are NOT type 12 but are type 9.

 

[aw113sgte]

Well that sucks, my 2003 A1 rear brake chamber diaphragms are NOT type 12 but are type 9.

Service or parking diaphram? I heard they changed through the years too.

 

[GeneralDisorder]

Well that sucks, my 2003 A1 rear brake chamber diaphragms are NOT type 12 but are type 9.

Interesting!

The TM says it's an X24-3276J-10 which I assume would be a type 10.

 

[Keith Knight]

Service brake.

 

[Keith Knight]

The old diaphragm had 9“ on it as well.

 

[GeneralDisorder]

Yeah looking at old posts it does seem to be a 9/12 brake can. Later trucks like mine are apparently the 12/16 brake cans.

 

[GeneralDisorder]

In the interest of tying things together..... It would seem that my use of the older A0/A1 pedal valve assembly ties in with the larger 12/16 brake cans on the A1R to provide quite a bit stronger brakes. I LOVE the way they work together.....

A1R brake pedal valve up(down)grade.

Those of you who have not driven an A1R or A1P2 probably will not understand this post. The C7 trucks (serial #100,001+) including both A1R and A1P2 have a different air brake pedal valve and if you have driven A0, A1, and A1R you may have noticed that the A1R trucks seem to have a brake pedal...

www.steelsoldiers.com

Might be possible for the A0/A1 truck owners to swap over to 12/16 cans and get the same enhanced braking. Takes way less pedal effort. Hopefully I'm not committing some cardinal sin by mixing and matching air brake system parts here. It works and it feels great so.....

 

[aw113sgte]

@GeneralDisorder did you glue the diaphragms back to the plunger? Wasn't expecting that when I opened mine up and noticed they were glued to it

 

[Mullaney]

@GeneralDisorder did you glue the diaphragms back to the plunger? Wasn't expecting that when I opened mine up and noticed they were glued to it

.
No. No need to glue the diaphragms!

 

[GeneralDisorder]

@GeneralDisorder did you glue the diaphragms back to the plunger? Wasn't expecting that when I opened mine up and noticed they were glued to it

No did not apply any glue. I noticed that as well. Seemed redundant so I didn't bother.

 

[aw113sgte]

Did my fronts, super easy to do. Did use a wire wheel to knock down the sharp pieces of glue.
Fronts were in great shape, not a single crack anywhere. May just keep a few spares and not worry about changing the rears.