1078 LMTV air brakes COMPLETELY inoperative

[porkysplace]

I didn't get far passed changed underwear
Scary read

That probably came after removing seat cushion.

 

[frank8003]

Here's my best guess - you've got pockets of moisture throughout the system. It's frozen. This may trap high pressure air in the spring brakes not allowing them to deploy, or it may just block the moving parts from moving.

On the service side, you also have pockets of moisture. This prevents the air pressure from reaching the cans and actuating the brakes.

Or the moving parts may just be frozen in place.

Either way, the solution is to get it warm and working before moving it. Once warm and working, relocated to somewhere you can work on it, purge the air system and rebuild/replace the air dryer.

Gee, did this happen to my military people?

 

[sue]

The “Springs” your diaphragm? Cans might have
been frozen so that would explain why there was
no movement. With air or with out. I have seen it
although rare on big trucks, if it happens again see
if you can manually actuate a brake. That might also
explain you might have a brake or two dragging
and getting hot, hence the smell. Just a guess?

 

[Doug Roberts]

purge the air at the end of the days use everytime you run the truck , not every few days.

 

[Suprman]

This happens on lmtvs. It happened to me. Had brakes then didn't have springs only service brakes. Which don't stop the truck on their own at speed. And then they just came back. I replaced the anti-compounding valve and the treadle valve and the problem went away. The tube fins air dryer puts a lot of moisture into the system. Get a better one. Take off air lines one at a time from all the valves blow out any gunk built up over time.

 

[Jerds19]

purge the air at the end of the days use everytime you run the truck , not every few days.

Doug, we only use/move the truck about once a week, so we do only purge the lines on days when we use it.

 

[Jerds19]

Got ahold of person who had done maintenance on the truck, the air dryer was not serviced, so we will start there, we will upgrade it to the newer/better one as I have seen many people on here suggest.

The truck is still sitting where we parked it, with the brakes locked on, so we cannot even move it. We'll have to wait for some warmer weather then start going through it replacing things until they release I guess.

 

[Jerds19]

And thank you to everyone that took the time to read reply and assist with this issue. If anyone has any more ideas please don't hesitate to share them, I will also share the results and outcome with ya'll in hopes of helping others learn from our issue.

 

[Jerds19]

Wanted to update everyone, since this issue two days ago occurred in 20-30 degree weather we haven't touched the truck, now that it has warmed up to 45ish degrees we decided to go out and start working on it, and low and behold everything is working perfectly fine.
Service brakes work fine.
Emergency brake works perfectly fine.
The air leak in the left rear wheel is gone.

So as many people suggested it was obviously temperature, and likely ice in lines induced. To the best we can figure is that the brakes froze in the 10-20% applied position, so driving it for 10-15 minutes caused the brakes to fade and fail entirely.
As many people suggested also the air dryer has not been touched in many many years at the least.
So unfortunately we don't know EXACTLY what the problem was, but we will be pulling lines and purging them all individually and servicing if not replacing the air dryer before this thing moves more than a few feet!

I'll update ya'll once it's all done, but really at this point since everything is working fine it will really just be the equivalent of good maintenance being preformed.

 

[NDT]

I don't think the air side of the brake system is what froze up, rather the pushrod and wedge within the wedge brake actuators (all of them).

 

[Jerds19]

I don't think the air side of the brake system is what froze up, rather the pushrod and wedge within the wedge brake actuators (all of them).

If this is the case, what can/should we do to prevent it from happening again? I obviously don't know much about these brake systems, is this something we can service/lubricate/adjust or does it need to go to a heavy truck shop to address this?

 

[NDT]

If this is the case, what can/should we do to prevent it from happening again? I obviously don't know much about these brake systems, is this something we can service/lubricate/adjust or does it need to go to a heavy truck shop to address this?

Just reading up on this myself, the mfgr standard lubrication interval for wedge brake components is 160000 km or 12 months, whichever comes first. Use NLGI grade 1 grease.

 

[bikeman]

I don't think the air side of the brake system is what froze up, rather the pushrod and wedge within the wedge brake actuators (all of them).

It's in the lines...

https://www.nsncenter.com/Library/PSMAG/PS_589?PageNumber=5


This is a pretty common issue with the trucks. It was big deal in Korea every winter.

 

[Suprman]

There is a tm troubleshooting flow chart for brakes do not apply