m923a2 brake issue... help/advice needed

[rory1919]

So i've searched through the forums but ive not found what im looking for. ive read through some of the TMs and not found what im looking for but maybe im just missing what to look for.


I have driven larger truck with air brakes in the past but never had to do any maintenance on them.

i drove my 5 ton home form indianapolis with no issue. everything seemed to work like a dream. halfway through the trip the CTIS lights started all flashing instead of being one button selectable. one of the tires has a leak and the CTIS still worked to inflate that tire after the fact.


ok so here we are 3 weeks later and i need to move the truck. the bad tire is up on jack stands to reduce and pressure or future damage to the tire. So i start the truck and let the ctis inflate the tire again. all is fine. I remove the jack stands. but the truck now won't move. the brakes are locked up. I moved the truck a bit to see if one tire was locked up and others free (looking for a skid mark in the grass) not sure of this would even work but made sense in my novice brain. this did not show any difference. and for how much resistance there is, i couldn't imagine that it is only one wheel.

the air system is burping extra gas out like i am hitting the brakes every few minutes.

oh yeah both air tanks hold steady at 100 psi. (seems like most brake issues listed here have issues related to the air pressure)

emergency brake is down and i never engaged it.

brake override knob is pulled out in the normal position.

any suggestions? am i just a dummy and am missing something normal and simple?

Rory

 

[Coffey1]

The valve on the hand brake may not be releasing the spring brakes.
The hand brake is two braking systems one is a drum brake on driveshaft the other is the rear spring brake.
Mark hose's and remove the valve and put some air gun oil in vavle and get the valve working again.

 

[rory1919]

as soon as i have a dry day i will try that. right now its been raining buckets here.

 

[Coffey1]

By the way it is in the Tm but a pita to find took me a while.
Also if you need help my # is 704-534-4486
Name is Ken

 

[rory1919]

where in the TM? if you can give me an idea. thanks again for the help.

also is this a tough thing to do or crawl under the truck and spend about 30 minutes? just trying to plan for the work. if its a quick job i'll just throw a tarp down and deal with the mud

 

[Coffey1]

All the work will be inside cab

 

[brasco]

Rory,

How much time do you give between releasing the parking brake and before you try to move? I have one truck that takes a long time for the air to bleed off the brakes and I need to wait 10-15 seconds before I can move. This is one thing I need to fix on mine but haven't so far since it is just a minor nuisance at this point.

If you have been trying to move immediately after releasing the parking brake, try waiting a while before moving. It might not be your issue but worth trying before you tear into anything major. I can't believe that you have a big problem if it worked fine the last time your drove it.

You may also want to loosen the tension on the band brake as well. I tightend it too much one time and the spring apparently held the brake on even with the lever fully down.

Good luck.

Don

 

[Coffey1]

The valve is not a major problem it took a friend of mine who is 70 year old about 30 min to fix.
It's really not a big deal .

 

[brasco]

Rory,

How much time do you give between releasing the parking brake and before you try to move? I have one truck that takes a long time for the air to bleed off the brakes and I need to wait 10-15 seconds before I can move. This is one thing I need to fix on mine but haven't so far since it is just a minor nuisance at this point.

If you have been trying to move immediately after releasing the parking brake, try waiting a while before moving. It might not be your issue but worth trying before you tear into anything major. I can't believe that you have a big problem if it worked fine the last time your drove it.

You may also want to loosen the tension on the band brake as well. I tightend it too much one time and the spring apparently held the brake on even with the lever fully down.

Good luck.

Don

Rory,

I just re-read your orignal post and I missed the part about never engaging the parking brake. I would highly recommend getting into the practice of engaging the brake every time your park the truck. The truck will roll away in Neutral! Don't ask me how I know.

Don

 

[rory1919]

i have the wheels blocked because of the jacking up and all.

I try not to use hand brakes on anything until i know the condition. one of my first cars, it broke the first time i used it.

 

[Trailboss]

I have a M931A2 that will sometimes not release one or more wheels if it sits for a week or so. When your air gets above 60-70 psi, take a hand maul or sledge hammer and tap the hub ends of the stickking wheels. If that doesn't release the spring brake, make sure the parking brake is set and reach in behind the tire to whack the drum. You may have to repeat this a couple of times.

 

[rory1919]

Twas totally the issue and quickly resolved. Thanks guys!!


rory

 

[Coffey1]

Which one valve or sticking drums

 

[rory1919]

Appears that it was the valve.

Little airtool oil and let it run for a bit.

Real test set was engaging and disengaging the hand brake with no air release sounds. And of course the warning bell that the novice in me was sure it was still just building air in the tanks.

Maybe my buddy who was checking it out pulled the lever and released it while looking it over? Whatever you guys helped!

R