Brakes locked - Dual airpack

[np2ij]

I looked and read previous posts on brake issues but none on the dual air systems on the Air Force m35a2.
After purchase of the truck, we put around 10 hours on it, the brake pedal was stiff and required some force to activate the brakes. Well the next trip I fired up the truck and during the light check, the brakes locked up when pressed under full air pressure and did not release until I drained the tanks of pressure. Troubleshooting we found that air was coming from the service gladhand and from the vent by the air governor . we replaced both airpacks with used but unknown ones. Same situation.. we are in the process of rebuilding the airpacks. The hydraulic side looks good, no leaks noted. We have found that the system and airtanks had plenty of rust and moisture in them, not as well maintained as the TM recommends I think.
Most of the forum info is on the single airpack system. does anyone have experience with the dual setup? Also what I am concerned about is there any other place in the system that would allow the air side to be pressurized ? SMARPI9-2320-209-14P is engaging night time reading, but a little light on the troubleshooting. Of course the up side is that we have gotten really good at swapping out the airpacks and bleeding the system

 

[73m819]

check that the peddle is adjusted so that the M/C goes ALL THE WAY BACK, if not it will not allow the fluid to return to the chambers. where the peddle linkage connects to the M/C DISCONNECT, make sure the M/C control rod is ALL THE WAY BACK, then adjust the peddle linkage TO the M/C

 

[porkysplace]

Are all the brakes locking ?

 

[np2ij]

Are all the brakes locking ?

brakes lock and release only when air pressure released

 

[DeucesWild11]

This was my first problem with my truck however I did not have a dual system. It sounds like you are on a good course of action rebuilding both air packs. When I rebuilt mine that took care of it but then I was loosing pedal pressure so that led me to rebuilding the MC so now I am all set. I think when you rebuild the air pack.. all of it.. hopefully you will find your problem. Remember to bleed out the whole system starting with the Airpack(s).

Note: I didn't really have any "Ah ha" moments when rebuilding them so if you are not seeing anything noticeable doesn't mean it's not in there somewhere, however I did have a few things I saw that may have been the issue. Here is my thread if it helps you out.. http://www.steelsoldiers.com/deuce/82753-my-airpack-rebuild-photos.html

 

[RedbeardTheZombieHunter]

Open the left gladhand valve and then try it.

 

[Floridianson]

Hope you get it figured also at napa they have air tool oil and air tool oil and clearner. It's in a white bottle and I like this stuff over just the plane air tool oil.

 

[np2ij]

Open the left gladhand valve and then try it.

Air passes from LH fitting and brakes still locked. Will replace the air packs with rebuilt ones on Sat afternoon. Then check the pedal adjustment at the Master Cylinder.. Anyone else have info to pass?

 

[np2ij]

Well, identified the problem.. rebuildable..?

 

[dezert ratt]

it will buff out

 

[wsucougarx]

Yowza!!!

 

[DeucesWild11]

And that's why they tell ya to drain the air tanks after each use.

I'f you have a sand blaster use dry baking soda very soft not as abrasive as sand or other blasting materials. They use that to remove paint on fiberglass, that may help. It' all depends on how scored up the cylinder is. Most of the rubber parts take care of the seals.. Make sure you replace all the items in the rebuild. There should be no left over parts. Sometimes you can't see all the parts you need to take apart at first glance..

 

[np2ij]

And that's why they tell ya to drain the air tanks after each use.

I'f you have a sand blaster use dry baking soda very soft not as abrasive as sand or other blasting materials. They use that to remove paint on fiberglass, that may help. It' all depends on how scored up the cylinder is. Most of the rubber parts take care of the seals.. Make sure you replace all the items in the rebuild. There should be no left over parts. Sometimes you can't see all the parts you need to take apart at first glance..

We figure this is the way the truck came out of GL. we drain the airtanks after every use and have only put a few hours on the truck.

 

[DeucesWild11]

I am sure that's how you got it, didn't mean to insinuate that it was because you didn't drain the tanks regularly. There was a lot of weird stuff like that with my truck when I first got it. I drained almost a quart of water out of the fuel filters and the primary filter wasn't even in there!

Glad to see you found the problem!

 

[np2ij]

I am sure that's how you got it, didn't mean to insinuate that it was because you didn't drain the tanks regularly. There was a lot of weird stuff like that with my truck when I first got it. I drained almost a quart of water out of the fuel filters and the primary filter wasn't even in there!

Glad to see you found the problem!

All good DeucesWild11..!!
Well we made progress, 1 rebuilt pack installed and were making good progress toward a test drive until i broke the brake light switch off.. i guess i do not know my strength.. Next weekend will get back to it.

 

[DeucesWild11]

Good time to do the brake light switch upgrade, Here is a thread I posted when I broke mine off.. http://www.steelsoldiers.com/deuce/87241-brake-light-switch-upgrade-question.html It's a good thing to do safety wise. I just happen to snap mine off as well and glad I did the upgrade.. Let me know if you need more info..

PS: Mine may look a little different as I do not have a air line running to the back of the truck for the glad hand. My truck has a lot of things in different places since she used to be a Firetruck..