brakes locking up

I was driving, 60 mile trip. At the end the brakes locked down. I was able to get home but were dragging real bad. Air would come out of the service hook up on the rear when I opened the valve. What is causing this and how to fix.

Brakes

I have heard/read that the air packs have a tendency to stick if the trucks are not driven a lot. It might make sense (I am guessing) that if the master cylinder/ air pack sticking and not releasing then air would come out the line because the brakes are partially applied. You might try taking the Allen wrench plug on air pack) out and squirt (some posts long ago recommended Permatex Jack oil) some lubricant in there and try applying the brakes numerous times. The plug wouldn't come out on mine so I took the large pipe off of the rear of the air pack off and put it in there. Knock on wood, no release problems. Worth a try, the price and time to do is right. Good luck.

RE: Brakes

ditto but for the cost of a rebuild kit vs. peace of mind and safety... I'd go for the rebuild...

RE: Brakes

Had the same problem on mine. The airpack was not venting the air on release. I ended up getting to crawl under and break the fitting loose to bleed down the last of the trapped air until I got a good airpack installed.

RE: Brakes

Check the airpak vent line before doing something drastic, it vents together with the MC and fuel tank into the crankcase breather vent....

RE: Brakes

what I would like to know if it vents the MC as well could it be if I had my MC overfilled it would vent out the acces brake fluid I had it comming out pretty good when I got done bleeding my brakes but noe it has started to be hardly any at all and my MC hasnt lost much brake fluid since?

Brakes

Bjorn, I almost remember seeing a safety bulletin about separating the master cylinder vent line from the rest due to brake fluid contamination from something else hooked to the vent line or water. Am I dreaming? Thanks

RE: Brakes

There is a bulletin in PS magazine and its on the site here somewhere.

RE: Brakes

Found it.
http://www.steelsoldiers.com/index....rpak_vent&name=gallery&include=view_photo.php

Thanks for the info

Thanks Kenny for posting the link as well as the expert guidance on the TMs. I found just what I need, although it looks as if I will have to get a few more parts before tackling this job. Maybe you should have the title of Steel Solders Super Librarian or King of Information Recovery! Thanks again

Rich

RE: Thanks for the info

Ok I moved the truck today around the yard and brakes worked ok. I drive the truck at least 4 to 5 times a week, about 30 miles or so. have about 2,500 to 3,000 miles on it sence I got it several months ago. Everything has been working ok until yesterday when the brakes locked and would not release. the brake peddle was solid with no movement.

RE: Thanks for the info

I just drove 125 miles out to 29 palms for a camp out and the deuce brakes locked up on me as well. I have noticed when I drive long distances, the brake pedal gets higher and higher. This time the brakes locked up and I had me some locked up, smokey, toasty brakes. I bled the air tanks with no success. I then broke a back brake cylinder and wolah! The brakes let go. A bunch of fluid shot out the bleeder valve. My fluid was yellow/amber. I am being told it's old brake fluid and I should start by bleeding my cylinders until they all bleed purple. I am also told to add a thimble of air tool oil behind the square plug in the back of the air pack.

I am being told the check valve is getting stuck.

Am I on target??? Many thanks.

RE: Thanks for the info

BigMike that's the thing. You DO want to add the air tool oil to the square plug for lubricating the Air Pack. Also, look at splitting your vent system per the PS magazine.

RE: Thanks for the info

mine did this recently. it would lock up and stick when you hit the brakes but would work itself free while driving but it was undriveable due to the brakes bein stuck. if you opened the service side the brakes would work just like normal. i pulled the allen plug and juiced it up with marvel mystery oil and went and some panic stops. it made it driveable again but i still need to do a rebuild on my airpak. make sure you have an open area for panic stops, my truck liked to slide sideways when i locked up the brakes at 50

RE: Thanks for the info

I found trash in the master that was not allowing it to release. I thought it was the air pack but when I opened it up it still had the assembly grease in it.

RE: Thanks for the info

Does anyone know the TM that details the brake system? I'm still trying to figure out exactly how the air over hydro works.

RE: Thanks for the info

One of them is the TM 9-2320-361-20

Temporary fix for air pack problem

I've been waiting for somebody to post the problem of their brake booster locking up the brakes and want to show how I handled the problem. I was up in Live Oak picking up a 'C' turbo from Matt at Green Gems Army Surplus Depot and he described having similar problems with one or more of his trucks. He pulled out an air pack and showed me the plug on the back and said he had to pull the plug to relieve the air pressure which kept the brakes from releasing and that got him on the road again. I thought about this for a while since I had this problem too, I hooked up a cheater which allows me to monitor the air pack while I am driving and also purge any air pressure from the pack if I am not on the brakes. You can also use this copper line to feed air tool oil into the air pack, like another member mentioned, without having to crawl under the truck. Very simple installation and it really works! Even if you leave the valve open while you drive, you can still stop the vehicle but I always close the valve when I am in any kind of traffic at all.

RE: Temporary fix for air pack problem

so I guessing that all of us 5T owners should also be adding air tool oil to the 5T airpack as well? seeing as how its more or less the same system, just larger?

I see that TM 9-2320-209-34-2-1 chapter 12 details the rebuilding of the hydro pack. But I was really looking for something that details how it works. It looks like when you push the pedal, fluid is pushed into the front end of the hydro pack and opens a mechanical valve which lets air into the chamber (the end where the square plug is) and this pushes the piston which in turn pushes against brake fluid which applies the brakes.

How the air escapes, escapes me

Putting a gauge on is a clever idea but is there an audible sound?? How else does one know?? I guess, if you pump the pedal, it should not get higher and higher, it should always go to the same place??

BTW, awsome pics and explanation.