1083A1 - Brakes do only half release, ABS light is on!

[AKAustria]

Hello fellow FMTV enthusiasts!
I am out of ideas, and after reading through countless threads for the past two weeks, I decided to ask for help!
Here is what I have going on:
M1083A1, Year 2000
One of the two brake pads on the front, left wheel does not release.
I can and have driven it a few hundred feet, but it didn‘t feel right and the truck is also pulling hard to the left because of that.
There seems to be a small leak of some sort on the inside of the left front wheel, not sure where that could come from though.
A friend of mine believes that all brakes seem to be only half released, but I am not sure about that.
I checked...
Glad hands are free of obstructions and all installed;
Air pressure is good on front and rear (120psi);
Parking break does make the swishing sound when activating/deactivating as expected;
I tried using a hammer but no luck. But the brakes are not stuck anyways. They are just not releasing;
Could the ABS light on the instrument dash have anything to do with any of that?
I have downloaded every single TM I could find and the amount of information available is daunting.

I am SO ready to drive it for real, and so excited that I finally have figured out the starting problem by grounding the starter solenoid. THANK YOU SS!

There is still so much to address but being able to actually take it on the road or even pull a trailer with it for a few miles would be „epic“!

Anyone any ideas?!

Thank you!!! Have a great weekend everybody!

 

[NDT]

The front brakes are not part of the parking brakes. Does the front brake release with zero air pressure in the system? That would mean air system issues. If brake still engaged with or without air, you have a stuck plunger mechanism on the brake air canister.

 

[AKAustria]

They do not!
I will go after the plunger mechanism (hopefully today)!
Thank you!!!!

 

[Suprman]

I believe some a1 lmtvs had some sort of hydraulic front brake setup. You may have this.

 

[AKAustria]

It certainly appears that way. I am still in research-mode on that.
On another note - I have found and downloaded more than one dozen of TM‘s, but came to realize they are for the 1083, and NOT the 1083A1!
Any pointers in the right direction?
I assume that the ABS light is directly associated with the ‚stuck‘ break shoe, which would make sense.

 

[Suprman]

They have made alot of odd variants over the years. Somewhere on your truck will be an air to hydraulic brake converter. I would think the abs light could be related to the wheel issue. It looks like oil dripping down. Do you have air brake cans on your front wheels also or is it just hydraulic? Post some more pics of the fronts if you can. What engine do you have?

 

[coachgeo]

.... found and downloaded more than one dozen of TM‘s, but came to realize they are for the 1083, and NOT the 1083A1! Any pointers in the right direction?...

For "LEGAL" A1 manuals PM this fellow mototech. Not sure the hydraulic type brakes made it into any manuals but maybe?

 

[AKAustria]

I have the CAT 3126 engine.
I do have a air brake can.
I won‘t get to the truck before a few hours but will attempt to take a better picture.

It seems as the lower part of the wheel is leaking only.

 

[coachgeo]

... It seems as the lower part of the wheel is leaking only.
View attachment 767211

sounds/looks like she been sitting a lot from what you described..... thus, there is this thing called gravity that makes it look like only lower part is leaking. Then when you drive it will get spin art design on the tire.

 

[Floridianson]

Don't know if this is the case but if the front brake diaphragm gets a hole in it will push grease out of the wedge assembly. Blows the seal. That plus as said maybe above stuck plunger too. You might get lucky and be able to get the drum off to look see and service. If the drum is to tight you might have to disconnect air can brake line. Knock the jam nut loose on the air can shaft assembly and unscrew the whole thing to get the brakes to back off so you can get the drum off. Then fix problem.

 

[Ronmar]

You said one of the two brake pads is stuck... Does the other one move when you step on the pedal? If so it sounds like the actuator that the wedge pushes on is stuck. Strip it down, they are simple, just big... Also make note that the shoes are installed correctly, the back plates are stamped as to which end goes toward adjuster and which end goes toward actuator...

 

[wandering neurons]

The LMTV TM for the A0 models, the -365-20-3, section 11.2, shows a manual adjuster for the front shoes. Like any old car with drum brakes, the adjuster provides a preload in the shoe-to-drum distance. The automatic adjuster completes the rest.
Seeing how badly the fronts were set up on my M1081 A0, I'd almost guess that the shoe that's stuck is actually overadjusted using the manual adjuster, and jammed against the drum. The leak could be something else entirely, like one of the internal axle seals letting diff lube leak out, or coming from the gear reduction hub.
My $0.02...

 

[Ronmar]

Seeing how badly the fronts were set up on my M1081 A0, I'd almost guess that the shoe that's stuck is actually overadjusted using the manual adjuster, and jammed against the drum.
My $0.02...

3 of the 4 shoes on mine were installed backwards when I got it...

 

[AKAustria]

Yes. I have come to the same conclusion after looking at the setup from above and the engine side.
Getting that wheel off with one brake shoe being so tight against the drum will be next to impossible I am afraid.
I might have found the reason why this truck got ditched?!
I am going to put the truck on blocks and get started going after that wheel...

 

[AKAustria]

You have definitely a point. From the little I know so far, it would be my most preferred solution for the stuck brake shoe and evidence of leaking fluid coming from the wheel.
I am just not too excited to open up a perfectly tight air line/system to go after an unknown problem.

 

[AKAustria]

Any way to tell whether that‘s the case without taking the wheel off?
Not that I could fix that without taking the wheel off, but it sure would be a nice motivator if!

 

[AKAustria]

I completely forgot to check that when I had a buddy come by. Darn!
From the sounds of it, I will be taking off a very heavy wheel tomorrow, and I am kind of excited and nervous about it.
It really seems that this is the only way to get to the bottom of this.
Wish me luck!

 

[Ronmar]

You should be able to see the state of the adjusters. You may be able to loosen the adjuster on the tight shoe to help you get the drum off... Good Luck!

 

[AKAustria]

you should be able to see the state of the adjusters. You may be able to loosen the adjuster on the tight shoe to help you get the drum off... Good luck!

thank you!!!!

 

[Floridianson]

The gear oil from the outer hub would have to go through the all the CTIS high pressure seals to reach the inner grease seal. Could happen but we did have an OP that the diaphragm did leak and knocked off the wedge assembly adjuster seal. Could be the inner hub seal leak but it is not just a single lip seal. If it was just the plunger stuck buy taking apart the air can and see if the plunger is stuck down you might be able to pull it out. The self adjusters also is a good idea but check the plunger for sticking also. Hope it will go easy getting the drum off for you.