locked down

[smoothnu]

I have a M989 trailer and the brakes are locked down. I have 90psi on my pressure gage , but they still won't release. This trailer has a mysterious button on the drivers side of the tongue would this have anything to do with my problem? Thanks for any help.

 

[army_nurse]

we had that happen all the time in the MLRS unit i was in. back up and see if they release. if i remember right that is how we got them to release often. you also need to check and make sure the air breaks are in good working order. check the s-cam and ensure that they are moving. water was the problem 9 times out of 10. you need to ensure that you watch this one. one of my soldiers drug a whole in one pulling it locked up one night on a ammo run not knowing it was locked up while in black out drive. these are good trailers and you can haul a crap load on them as well. hope this helps


Mark

 

[smoothnu]

I have tried backing up with no success. Time to take airlines apart and see if I can find some kind of blockage.

 

[Ruppster]

I take it the trailer has dual chamber air cans on at least one of the axles? Have you had someone pull the brake release valve while you watch the arms on the brake chambers for movement? If you have movement of the arms but the shoes don't release then they are rusted to the drum. With the parking brake released and wheel chocks under the trailer and truck take a good sized hammer to the brake shoes to free them. I've had this happen a few times with trailers that have sat for a while. Or you can bypass the emergency parking brake feature of the air cans by hand with the special bolt and nut assembly that's on the side of the dual chamber air cans.

Might also want to try releasing the brakes with at least 100 psi of air pressure. I have one trailer that will not release the parking brake unless the air pressure is about 110 psi when I pull the release valve. Once they are released the pressure can drop down to 70 psi and they will not grab. It's just picky getting it to come free the first time. After that its fine.

Ruppster

 

[Alredneck]

Ruppsters on to something. I would check the brakes to see if they are free and the cams are moving like they are supposed to. We had problems like this with our M872s when I was a 63S in my begining Army days. Water gets into the system form everywhere and tends to make everything rusty when it sits for a long time. Make sure you are bleeding your tanks after you get done using it and drive it around if you go through any deep water to dry things out. Goodluck!

 

[nk14zp]

Are your air lines hooked up right?

 

[smoothnu]

I thought about reversing the lines, but both hoses are not long enough to swap from one side to the other. However, one of the lines is in fact long enough to make the trip to the other side. I tried it and the brakes released.Why in the h#$% these lines would be hooked up like this I don't know. Time to buy longer hoses so I can cross them over one another into a square knot so I can get them hooked up to the right service line on the truck.

 

[Floridianson]

Digging up an old thread but from what I gather from mine is. The button valve is use when the trailer has air in trailer tank and no truck hooked up. The parking brake can be put on or taken off with the valve. Of coures with duel chambers without air in the tank or system the parking chamber will be on. When you hook up the truck air lines and pressure up the trailer system and push in the trailer parking brake in the cab of the truck it over rides the button on trailer and the button will stay in the out pisition. Try and push it in an it will just pop back out.