Intermittent Brake lock-up problem

[Awesome Possum]

I've been having an intermittent problem with one or the other of the rear brakes on my Bob just locking up when the air system is up to pressure (90-120psi). It doesn't do it when I'm driving, though it has left me stuck at a few intersections. We've adjusted the brakes according to the manual, and also just moved them all the way out. This was today and it has happened before. (Since my air steering dumps excess air in a right turn I can always get it moving by dumping the air down to 60psi or so. Not a fix but beats sitting at a light unable to move!)

Yesterday we took it for a drive and it did great. Other times the only problem is that the rear brake locks for a second or two before releasing. It may also be that it depends on whether the truck is parked facing uphill or down in my driveway. A problem like this is very hard to diagnose when I only drive the truck once every week or two.

I don't fully understand how an air-over-hydraulic brake system works either, though I'm learning. It would seem it may have something to do with the airpac(?)
When it's up to behaving badly, it's like it's still delivering enough brake fluid to stop both of the rear axles even though there is just the one rear axle. BTW, we have experimented with brake pedal play as well to no avail.
HELP!

 

[Katahdin]

The air pac requires lube, start with that:
http://www.steelsoldiers.com/deuce/61605-how-world-do-i-service-my-air-pack.html

 

[DeucesWild11]

Possum, sounds like you are having the same issue I was.. a bad air pack, check your slobber tube to see if anything is dumping out of there.. If brake fluid is coming out of it then you'll probably need a rebuild because the fluid is getting past one of the seals somewhere and getting into the air side of the system. However try lubricating first as Katahdin said.. Here is a thread I dedicated to my Air pack rebuild if you wind up needing it.

http://www.steelsoldiers.com/deuce/82753-my-airpack-rebuild-photos.html

 

[Awesome Possum]

Thanks for the help and the link guys. One thing I didn't catch in the other thread was the type of oil to put in the air pack. Suggestions?

 

[DeucesWild11]

Use air tool oil.. That's what I've been told

 

[Awesome Possum]

I canlt find this air pak in my TM's. They show another style than the one I have. Could someone tell me if this is an old style-new style? Where would I lube this one?

 

[Awesome Possum]

I canlt find this air pak in my TM's. They show another style than the one I have. Could someone tell me if this is an old style-new style? Where would I lube this one?

Took off the skid plate and WHOA! There's a whole lot of connections under there. If I understand correctly, I can remove the end of the J Tube on the rear and get a few squirts of oil in there. Where would the oil go at the front end?

 

[scoutmanadam]

only the air side needs to be lubed, the other side has the brake fluid in it.

 

[DeucesWild11]

Jeff, that's different then the standard Airpack. I looked through Saturn Surplus and found what they call a Hydrovac, here's a pic. They have a rebuild kit for that as well Part No RN-25-P but it looks like it's currently sold out. What year is your Deuce, I am curious if this is from an earlier year, my Deuce is a '73

 

[Awesome Possum]

Jeff, that's different then the standard Airpack. I looked through Saturn Surplus and found what they call a Hydrovac, here's a pic. They have a rebuild kit for that as well Part No RN-25-P but it looks like it's currently sold out. What year is your Deuce, I am curious if this is from an earlier year, my Deuce is a '73

Yep, that's the one. The truck is an 85 AM General and was depot rebuilt in 95. Is it still a matter of lubing it, or are we looking at a completely different beast?

 

[DeucesWild11]

Hmmm I suppose you would still need lubrication. Seeing how you have a newer model mine being a 73 then I suppose you have the "newer Style" I don't know how that one is set up in the back but on mine there is a small plug on the back with a square head. I can just take that out and shoot some oil in there. If there is no plug then I suppose you could just disconnect the air line running back there and put some oil in there..

If you drive it allot and far distances, not just around town, I would probably just get the rebuild kit and rebuild it just for piece of mind.. and safety..