M1078 air brakes

[SUBARUMAFIA]

Noob here. If this is the wrong forum or if this question is answered somewhere else my sincere apologies. I recently bought a M1078 LMTV. If I use the brakes for any amount of time the alarms buzz, warning lights come on and I have to use the parking brake. Normal or do I have a leak somewhere? Keep in mind I can drive it. I just have to be careful not to use the brakes much.
Thanks in advance for any help or knowledge coming my way.

 

[simp5782]

Noob here. If this is the wrong forum or if this question is answered somewhere else my sincere apologies. I recently bought a M1078 LMTV. If I use the brakes for any amount of time the alarms buzz, warning lights come on and I have to use the parking brake. Normal or do I have a leak somewhere? Keep in mind I can drive it. I just have to be careful not to use the brakes much.
Thanks in advance for any help or knowledge coming my way.

Blown service diaphragm in a brake can or you have a bad relay valve dumping air when the service side is applied or a hole in a service side line

 

[NDT]

Air up, chock the tires, cut the engine, get momma to hit the brakes while you go sleuthin underneath. Will be very audible.

 

[SUBARUMAFIA]

Wow. Thanks guys. Great info. I’ll get under there and listen. I’ll post my finding.

 

[flyfishtrailer]

And just so you know, a post about an M1078 should be under FMTV present day conflict vehicles. Especially if you have more questions pertaining to an M1078.

 

[SUBARUMAFIA]

Oh I’m gonna have more questions. Thanks for pointing me in the right direction.

 

[Weldman]

Get some edumacation here on what is going on Air Brake Training

 

[SUBARUMAFIA]

Air up, chock the tires, cut the engine, get momma to hit the brakes while you go sleuthin underneath. Will be very audible.

Well I did exactly this. There is a leak on the back side of the rear drivers side wheel. I think it’s one of the hoses. I can feel the air coming out. Probably too much air for soapy water to be useful. Maybe let the air most of the way out and spray it when the pressure is low?

 

[SUBARUMAFIA]

1

 

[NDT]

Well I did exactly this. There is a leak on the back side of the rear drivers side wheel. I think it’s one of the hoses. I can feel the air coming out. Probably too much air for soapy water to be useful. Maybe let the air most of the way out and spray it when the pressure is low?

Whatever it takes to isolate the leak. Hope that it's not a diaphragm.

 

[SUBARUMAFIA]

Well I found the leak. Now I need to work out how to safely fix it. Thanks for all the advice and patience. I’m learning a lot here. First rig with air brakes.

 

[G744]

Use caution with the air pots like that in your photo.

The brakes are activated two ways:

The smaller device will use air pressure to apply them.
The larger device is a spring chamber, under considerable pressure that sets the brakes if air is lacking. Sort of a fail-safe and a good parking brake.

Given that, never loosen the clamp that holds the spring chamber together. Replacements are easily available at any heavy truck or surplus dealer.
Other than that, they are pretty simple devices.

 

[Floridianson]

Yep got to be careful working with any air brake chamber. Here looks like it is the service diaphragm so you could cage the brake spring chamber and change out the service diaphragm. Problem is most of these trucks have never had any of the diaphragm's changed so my self I would do both to that can. Would bet the 98% of people hurt when working on the spring brake side did not cage the can before removing the retainer ring. Then 1% over tighten/ broke the cage bolt. Then 1% cage bolt came unlocked. You do not need the 16 inch breaker bar to tighten the nut.
Did a write up with picks but can not find it on the board of doing both diaphragm's.

 

[Mullaney]

Well I found the leak. Now I need to work out how to safely fix it. Thanks for all the advice and patience. I’m learning a lot here. First rig with air brakes.

.
@G744 and @Floridianson are dead on the money! You need more information before you jump in and "just fix" the air chambers on any air brake system.

First of all : Think Before You Die. There is a spring behind the outward facing "cap" on the air chamber. That chunk of aluminum will knock you out cold if it doesn't kill you first. No Bull. You don't have the required caging bolt in it's holder in the picture that you uploaded. You really need that bolt before you do anything.

Technically you can remove and replace the complete "can" without the caging bolt, but this is a learning session. So please get yourself a caging bolt and know how to use it.




I added a few pictures so you can have a good understanding about what the caging bolt looks like and how it is used. Even some written TM instructions...

Don't hesitate to ASK QUESTIONS before you turn wrenches. Nobody here will give you grief or cajole you about this particular piece of truck repair. It's no joke for sure!

EDIT

I couldn't help myself... Added one more picture below. That big spring on the right is what is hiding behind the "cap" that is NOT bubbling in your picture. The caging bolt is inserted (from left to right in this picture) to capture and cage (secure) that monster spring.

 

[Floridianson]

In this case where it is the service side and not the parking brake side will make it easer. Air up the truck till the air dryer pops off and you have full air pressure. Have you cage bolt handy and nut working free. Flat ground and wheels chocked enough so truck can not roll. Release parking brake in cab. Install cage bolt and turn clockwise 1/4 till it is locked in. Pulling on the shaft up to keep it locked in place run the nut down finger tight then just a little more with wrench to keep it tight. Return to cab and pull or set parking brake in cab and now that can is caged and the rest of the parking brakes will hold the truck.

 

[kendelrio]

The larger device is a spring chamber, under considerable pressure that sets the brakes if air is lacking. Sort of a fail-safe and a good parking brake.

Given that, never loosen the clamp that holds the spring chamber together.

I call them the "Jesus spring". Mess around and you'll meet Jesus.

 

[G744]

Think about it: When not held back by air pressure, that spring locks the drum/wheel/tire of a heavy truck. Right now.

 

[Floridianson]

Think about it: When not held back by air pressure, that spring locks the drum/wheel/tire of a heavy truck. Right now.

Yep that is one bad spring. I just make sure when taking off the retainer ring I am not facing the can. I work with my body / face off to the side as much as I can be but still be able to reach the band clamp nuts with my ratchet. Then once the can cap is off I treat it like a loaded weapon always careful where I point it.

 

[SUBARUMAFIA]

Guys I can’t express enough gratitude for the advice and sincere concern for my safety. With your help I was able to successfully cage the spring and remove the air brake at the service diaphragm. In doing so I discovered that the whole housing was bent upward and the end of push rod was snapped off on the diaphragm side. It looks like a whole new unit is $500 ish but I’m not sure what I’ll do about the push rod. I’m attaching some pictures. The last 2 pics are of the end of the push rod.

 

[G744]

Probably done by a forklift at the surplus yard, moving or loading it.