Wile E. Coyote
Active member
- 392
- 73
- 28
- Location
- Lynden WA
Years ago we bought an M923 from an Ebay vendor, which was an ex-GSA USFS disposal. The spring brakes never worked, but it seemed to stop fine. I finally got around to it and...yeah. Just...yeah.
The spring brakes didn't work because, as per usual, they'd jammed on and someone at some point decided to tow it or drive it anyway, uncaged, neatly shaving a 1/16" valley off the brake pads. The adjusters were seized, which I expected anyway - but what I didn't expect was what I found when I got into the wedge system.
Basically, the wedge operating rod and rollers didn't retract after a brake application (one had actually shed it's roller, suspiciously.) Upon removing the brake chamber stalk and the operating rod and roller assy (see '2' in the hopefully att'd diagram) - the spring was nothing but a pile of rusty semi-circles, and the roller mounts were rusted thin. Pulled all the rest of the rear chambers and found exactly the same thing. Every single one of those springs was a pile of rotted jingling semi-circles.
I rebuilt everything. After looking at things I would say the truck had been up to the doors in water or some swamp for a *very* long time, because I can't see any other way those brake chamber stalks would've retained water to that degree, nor how such rot could've occurred to things like the auto-adjuster springs (which were nothing but iron dust when I disassembled it all.)
Really, there's no giveaway as to the condition of all this stuff just looking at the truck externally because the paint's great and everything else works...BUT...again, suspiciously, in the driver's compartment the floor had shattered at some point thanks to an impact at the bottom corner of the cab where it mounts to the frame, and there's a bunch of really bad farmer-style gas welding there and rust...in that one spot only. Then you get into the cab and the driver's seat bottom has clearly been immersed in water/ muck/ mire for a very long time, as the diagonal tubes of the spring-ride seat are both rotted right through where they mount to the floor plate. I don't know what the story was with this truck, but it must've involved a few beer, a broken compass, and a swamp.
Anyway, if you're doing brakes on your own M939 series - might want to pop off one of the air chamber stocks and check out the spring condition on item '2' there. I'll be doing that on all the other trucks here when I get time.
The spring brakes didn't work because, as per usual, they'd jammed on and someone at some point decided to tow it or drive it anyway, uncaged, neatly shaving a 1/16" valley off the brake pads. The adjusters were seized, which I expected anyway - but what I didn't expect was what I found when I got into the wedge system.
Basically, the wedge operating rod and rollers didn't retract after a brake application (one had actually shed it's roller, suspiciously.) Upon removing the brake chamber stalk and the operating rod and roller assy (see '2' in the hopefully att'd diagram) - the spring was nothing but a pile of rusty semi-circles, and the roller mounts were rusted thin. Pulled all the rest of the rear chambers and found exactly the same thing. Every single one of those springs was a pile of rotted jingling semi-circles.
I rebuilt everything. After looking at things I would say the truck had been up to the doors in water or some swamp for a *very* long time, because I can't see any other way those brake chamber stalks would've retained water to that degree, nor how such rot could've occurred to things like the auto-adjuster springs (which were nothing but iron dust when I disassembled it all.)
Really, there's no giveaway as to the condition of all this stuff just looking at the truck externally because the paint's great and everything else works...BUT...again, suspiciously, in the driver's compartment the floor had shattered at some point thanks to an impact at the bottom corner of the cab where it mounts to the frame, and there's a bunch of really bad farmer-style gas welding there and rust...in that one spot only. Then you get into the cab and the driver's seat bottom has clearly been immersed in water/ muck/ mire for a very long time, as the diagonal tubes of the spring-ride seat are both rotted right through where they mount to the floor plate. I don't know what the story was with this truck, but it must've involved a few beer, a broken compass, and a swamp.
Anyway, if you're doing brakes on your own M939 series - might want to pop off one of the air chamber stocks and check out the spring condition on item '2' there. I'll be doing that on all the other trucks here when I get time.
