Service Brakes not Releasing - Steel Soldiers::Military Vehicles Supersite

M35A2-AZ · 12-30-2011, 22:00

I had a problem with my M923A1 today. The service brakes are not releasing.

I went into town to the post office (about 10 miles) and I noticed that the truck was not getting up the speed. When I got to the Post Office I noticed the rear brake were hot. I let them cool as I tried to find out why they got hot. I looked at the cage brakes they looked ok, but I caged them anyway.

Thinking I had them released I headed home slowly. I stopped at about 3 miles and checked the brakes, they were hot again.
I looked over the truck as may wife pushed on the brakes. Now the brakes are locked up and will not release.

I called a friend on SS "Castle Bravo" and we talked a little and he said to drain the air tanks and see if the brakes release, they did?

So it is looking like the service brakes are not releasing after you push on the brake paddle and the more you push on the brakes the more they push.

Does any one have any ideas on the problem? I will try to start trouble shooting in a day or so.

F18hornetM · 12-30-2011, 22:33

I am not familar with the 923 brakes, but there may be a quick release or relay valve near the rear axle somewhere thats hung up. thats the way it is on commercial trucks.
Caging the brake chambers will only "hold" back the parking brake spring from applying. not the service side as you noticed. By letting all the air out of the tanks, the air eascaped the brake chmabers and the return spring pushed the service diapragms back, releasing the brakes...having said that, and depending on if you just let the air out of the tanks...might be a foot valve issue..thats the part the brake pedal is hooked to..
again this is just general air brake stuff, may not even apply to a 923
If i am not mistaken, are the brakes wedge type??

M35A2-AZ · 12-31-2011, 07:52

F18hornetM, Thanks for the reply and ideas to look at.
I did notice that the front brakes did not get hot.

Nonotagain · 12-31-2011, 08:27

I posted the PDF from Axletech the manufacturer of the wedge brakes.

putting zerk fittings on wedge brakes

Chances are that the two "barrels" that do the spreading of the shoes are rusted up.

M35A2-AZ · 12-31-2011, 08:49

Nonotagain, Thanks!!
But it was on all four rear brakes and not the front.

Nonotagain · 12-31-2011, 09:40

Quote:

Originally Posted by M35A2-AZ

Nonotagain, Thanks!!
But it was on all four rear brakes and not the front.

Try this one then.
Search for brakes and start around page 255

M35A2-AZ · 12-31-2011, 12:34

Went out this morning looked at some things. Started truck, checked brakes
worked ok. Started to drive around our block, got about a 1/2 mile and the brakes locked up again.
I am starting to think it maybe the ABS system.
Is there a way to disable the ABS system?

Derrickl112 · 12-31-2011, 12:46

He never posted if it worked or not....but does this help at all?

m936A2 brakes slowly lock-up...what gives?

rrrr · 12-31-2011, 14:53

It sounds like since its only the 4 rear wheel assemblies something is going on with your spring brakes. Perhaps some air issues ?

I would try caging all 4 rear spring brakes and do a slow test drive in an area that if the brakes stop working you'll have no issues. If the brakes still get hot than its not in your spring assemblies and we can try to help you trouble shoot other areas. Eliminate one system at a time.

My 932 had an issue and it ended up having an air line that was reversed with another air line. It took 3 days of trouble shooting to find that one. The TM's for this are not good either.

emmado22 · 12-31-2011, 15:14

Is your air pressure constant, and have you checked it with something OTHER than the guage on the dash? Sounds like an air pressure problem to me. My $$ is on a leak.