M105A2 Brakes Locked After the Pedal is Released

[AGE|kshaufl]

Before I get flamed for not looking through the TM's and searching the Forums, Been there Done That! I could not find anything close.

I have an M105A2 with the dual air lines. I had the airlines hooked up to my M35A2 with the hand brakes released (wheeled freely when moving it around by hand). I attempted to pull the trailer out of where it was parked and the brakes locked up. Both of the glad hands were attached properly and the valves open. I shut the valves off and bled off the air from the tank and the brakes released.
If I moved the trailer with the air on and did not hit the trucks brakes, it moved fine. As soon as I hit the brakes in the truck the brakes locked on the trailer and did not release until I opend the petcock on the bottom of the air tank on the trailer.

Does anyone have a clue on what is wrong? The TM's did not mention this problem and neither did the forums. I am going to assume that the relay valve has something wrong with it?????


I would greatly appreciate the help. Thanks in advance.

 

[jwaller]

sounds like the relay valve might be sticking.

 

[AGE|kshaufl]

That is what I was thinking too. I will pull it and attempt to clean it and put back together. Are you aware of any rebuild kits for it or just find another one?

 

[gimpyrobb]

Swbradley should have that. He is parting one out right now.

 

[nk14zp]

Are you positive the lines are hooked up right?

 

[Recovry4x4]

Inverted air hoses can cause that. If not then its a relay valve issue. Take it off and take it to a truck supply, they are not military unique.

 

[davidkroberts]

man that sounds like the hoses are inverted. I know you checked it but are you sure the motor pool didnt screw up the plumbing at the shop at some point.

 

[kurtkds]

I had the same problem with mine.

I had the lines swapped, I assumed that the lines went straight across passenger side to passenger side driver to driver.

I crossed the lines and the brakes worked as they should. So I immediately got the paint out and marked the gladhands.

 

[3dAngus]

That would be ONE QUICK FIX.

ie. if it works...

 

[AGE|kshaufl]

No one said Army Mechanics were smart. Although it could have been Depot that did the work which may have been a civilian contractor. I hope the later.

Looks like they installed the relay valve upside down which in turn caused the lines to be hooked up inverted. I didn't think that the relay valve was bad because it looks brand new.

I'm let you know for sure.

 

[Ressoldier]

I can't tell you how many times I have had stuff come back from rebuild in worse condition then it went in. I once got 10 trucks back and 8 of them had been plumbed backwards. I hope that they just inverted the relay or that you had the lines swapped. Good luck with the fix.

 

[rosco]

The lines are NOT crossed. If they were, the brakes would be set/applied as soon as the emergency/supply came on. Its a combination valve that is the culpret: Its called a Relay/Emergency valve. It also acts as a "quick release" valve, and dumps the air from the brake chambes, as soon as the tredle valve is released. If it weren't for the "quick release" function, back there by the brake chambers, the air would have to bleed back to release by the tredle valve, and you would have the impression of dragging brakes.

 

[KsM715]

rosco, these trailers do not have brake chambers. They are not air braked trailers. I'm betting crossed lines.

 

[jaxsof]

Umm, the lines are supposed to cross, like the chains, so they dont drag or pull out on turns

 

[AGE|kshaufl]

I will enlighten all.

The "Relay Valve" was installed upside down, which meant that the service air was plumbed into the emergency air and the emergency air was plumbed into the service air. What was happening was when the brakes were applied it closed the loop and locked up the brakes. Thank God for a simple fix.

Thanks to all whom thought of it first.

 

[drgreg]

I will enlighten all.

The "Relay Valve" was installed upside down, which meant that the service air was plumbed into the emergency air and the emergency air was plumbed into the service air. What was happening was when the brakes were applied it closed the loop and locked up the brakes. Thank God for a simple fix.

Thanks to all whom thought of it first.

So crossing the lines would have been the field repair?

 

[AGE|kshaufl]

What I did was just unhook the lines and turn the relay valve 180 degrees and reinstall the lines correctly. Ill take a picture in the morning.