M932 Recovery?

[rumplecat]

Arrived at the forestry compound late as usual, hooked up the towbar and light set, caged(?) the rear axle brakes couldn't on the middle axle, looks like commercial air cylinders there, made sure everything is in neutral, then gave it a tug, both axles are locked, all eight tires are dragging. Six forestry mechanics are standing around and the best they could do was hook up the air lines wrong. Got to be closing time so I dragged the truck about 100 yards in grass and gravel and the wheels on the passenger side on both axles turned, rocking back and forth did nothing to loosen the wheels on the drivers side. When I hooked up air to the 932 I could hear the tank fill with air and the gauge would show about 45lbs of pressure along with a significant leak on the rear most brake cylinder on the drivers side rear axle(Gaged One). Have a look at the pics., I am heading back down there Saturday moring!

 

[ARYankee]

Dang. You don't have the best luck with that place. If I was home I would come by and give you a hand. I don't get back until after the 18th. Sorry.

In one picture it looks as though the bolt is missing to cage that brake.
Did you try and hit the brakes in the 932 when it was all hooked up?

 

[m16ty]

Carry you a long bar (about 3') and a sledge hammer with you when you go back. These M939 trucks are bad about the brakes sticking if left sitting for long periods. Release the brakes (with air or by caging), take the bar and go down beside the tire placing the end on the brake drum, hit the bar with a good lick from the sledge. The jarring from the sledge should un-stick the shoes from the drum. I've had to use more than one lick sometimes but I've always been able to un-stick the brakes on a M939 like this.

You can take a screwdriver or something and pace in the caging brake hole to see if the chambers are releasing or not. First check with the brakes set and then release them. The distance you can place the screwdriver in the hole will be quite a bit less with the brakes released if the chambers are getting air and are working.

You should be able to cage all the brakes (commercial or not). You may want to carry you some extra bolts if the chamber doesn't have one in it's holder or doesn't have a holder. The caging bolts can be had at any truck parts store. I'd be a little concerned flat towing a truck with all the brakes caged though.

 

[rumplecat]

The 818 has good brakes but I am going to take a couple of extra batteries to see if I can start the truck, the forestry guys believe it was driven in, the odd part was the brake you can see on the dash that is square and yellow says push in for off and pull out to set, it is out all the time when I applied air to it, you could not push it in and have it stay, it would just come back out when you let go? I also don't know why I couldn't build air in the truck using the 818, 40-50 lbs is all it would build? Also the locked up one is leaking pretty good! Would that be part of the wheel being locked up? Also the two middle brakes did not have the T bolts, and the bolts off a freight liner and another 900 series would not fit?

 

[MidnightDuramax]

Valve will not stay in if the psi is to low on the air. It is a safety feature for air brakes.

 

[doghead]

You did have the T-case in neutral, correct?

 

[212sparky]

Usually at 30 pounds of air is when the air valve pops out to set the brakes. On your chamber that is leaking, it sounds like it is the emergency side air line. If you could cap it you would probably build air.

 

[juanprado]

That is definitely a commercial parking brake valve. That is not the correct set up for a m939. The original is a spring brake bypass not a parking brake. I am not sure if they are internally the same set up? The brake lines could be plumbed differently now than original if they rigged a parking brake?

 

[m16ty]

Also the locked up one is leaking pretty good! Would that be part of the wheel being locked up? Also the two middle brakes did not have the T bolts, and the bolts off a freight liner and another 900 series would not fit?

I'd say there's a pretty good chance the shoes are stuck to the drum on the locked up wheel. Use the sledge hammer method I mentioned earlier to solve that.

I don't know about the caging bolts. I've never seen one that wouldn't fit. Are you sure there's not a bunch of crap in there that's not letting the bolt go in the slot? You may also want to carry a file with you to knock some off the ends of the "T" if it seems too wide.

If worse comes to worse, you could remove the brake chamber and that will release the brake on that axle if you can't get air to release them or the caging blots won't work.

 

[rumplecat]

I have a heavy rock breaking bar with a blunt end so I can try the shock them loose, the Tcase handle is flush with the floor and will not budge, I had to wave off a big forestry guy who was trying to strong arm it! I intend removing the front and rear drive shafts, which should be fun now that it is raining! What concerns me is the middle axle will turn on the passenger side but not on the drivers side? the same is true of the rear axle and it is caged! So the hammer approach may help on both, however the low air pressure and the parking break on does make me concerned that the middle axle may be locked because of that system, but only one set of wheels(drivers side. I am taking four extra batteries to see if the truck will start, there were no skid marks on the ground where the truck has been sitting, and they "think" it was driven off the trailer. But I have to move it this weekend, or come Monday the local bureaucrat will have me towed for $450 and $25 a day storage!

 

[rumplecat]

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