H-47 Brakes

[jaymundy]

Howdy! Got a brake problem on a HJ-47. I replaced a cracked brake line (front brake circuit, hard line from union on frame to union on front axle). I've bled the brakes and bled the brakes and bled the brakes. There's still air getting into the system. The line I replaced is good, no leaks at the unions. No leaks at the slave cylinders. I noticed a very small seep on the -rear- circuit at the master cylinder. However, when I bleed the left front brake it takes about three presses of the pedal to get fluid. Anyone have any thoughts? I'm stumped, other than stopping the seep at the master cylinder.

 

[Hltoppr]

Usually, when you get pressure after several pumps with the military drum brake systems on the troopies and H pickups, it indicates that the brake shoes are out of adjustment. Jack up each front wheel, adjust each of the shoes until it locks the drum from moving, then back the shoe off 5-7 clicks. This needs to be done for each shoe on the front, as there are dual wheel cylinders.

Once that is done on each side, see if your pedal has improved....

-H-

 

[amaurer]

I think he's saying that he has physically confirmed that the left front cylinder is filling with air, so its not an adjustment problem.

Back to the original question - the problem probably ISN'T the seep at the master. A leak there would introduce air at the top of the line, so the cylinders would still be full. If the cylinders are winding up empty, then its the cylinders that are leaking - replace them. You may not see a leak because, perhaps, you have an exciting brake-dust-and-fluid soup waiting for you inside the drum...

 

[jaymundy]

Amaurer,

Yep, that's what I was saying. I pulled the left front drum off...no real evidence of leaking, actually. I've decided to get cylinder rebuild kits for all the cylinders, front and rear and to have the master rebuilt, as well as replace several sections of line including the flexible line to the left front wheel which shows considerable wear. Maybe it's overkill but my basic plan is to totally rebuild the brake system. it could be like Hltopper was saying that the shoes are out of adjustment, but I'll tackle that when everything is put back together. I did notice when I pulled apart the cylinders I removed to clean them for transport that they were DISGUSTING inside. No evidence any maintenance had ever been done on them.