So I just picked up this project. Was my adopted Gpaws truck so it holds sentimental value as he has passed. Its a 65 M52A2 Truck needs a lot of work but i really need to start at the brakes. Peddle goes all the way to the floor when pressed. Don't see any leaks from the wheel cylinders but truck has been sitting awhile. Is there any specific way breaks need to be bled on these trucks? just wondering as I am assuming its a air over hydro type system. Any help would be great thanks.
I started by bleeding the master cylinder then the hydrovac then moved to the furthest wheel cylinder away to bleed to each wheel.
You don’t necessarily need air pressure built up. Whoever you get to pump the brakes make sure they are patient and go slow & steady. Pumping up the brakes only created air bubbles and you will never get them out.
After I bled the MC & HV I would open the bleeder valves and simply allow gravity to do most of the work.
Keep your brake fluid by the MC access door on the drivers side floor board.
Hopefully there won’t be any leaks! It would not surprise me if you need to adjust the brakes.
I used to slide the axles out so I could spin the wheel and feel the drag.
At the bottom rear of each backing plate are the anchor bolts with a nut. That bolt will move the brake shoes out or in. There’s a small “window” on the front side of the drum held in place by a nut. This window is where you’ll insert the feeler gauge to check show adjustment clearances. You’ll need to remove the outer wheel / tire from all duals to get your feeler gauge in there.
Loosen that nut on the anchor bolt but if the cam centric anchor bolt doesn’t move - do not force it. If it is locked up do yourself a favor and remove the hub / drum.
If it is hung up you’ll need to lube it while tapping in it - don’t pound or hit it hard or you’ll destroy those bolts. You might even need a little gear.
Inside the drum there is a clip that holds the shoe to the bolt. There is also a cup washer behind the shoe and there is a felt washer inside that cup. Too much heat & that washer is no good.
If my memory is good, the bottom clearance between the shoe & drum is 0.010” & the top i s 0.020”.
The top adjustment is another cam centric type bolt head. If you look inside the brake drum at the shoes you’ll see the cam adjuster. These will not turn 360. You should only be able to turn a little left or right.
As you adjust - tackle one shoe at a time. Alternate adjusting from top to bottom until you get them correct.
The top doesn’t “tighten down”. You make the adjustment and leave it. On the bottom however you need to use a 9/16” wrench to hold that cam bolt in position while you tighten down that lock nut. Can’t remember what size but I reckon it’s between 7/8 & 15/16.
If that lower anchor bolt moves you will need to readjust the clearance.
If you need to remove the anchor bolts a quick scrub with crocus cloth to the bolt & the bolt bore will most likely be needed. A smear of thick grease (peanut butter) or antiseize on that part of the anchor bolt that sits in the bore will keep it from setting up again.
After one shoe is done then move to the next. Then one wheel at a time.
It doesn’t matter which brake gets a mechanical adjusted first.
I’m certain there are some guys who will clear up any fog I left here and also provide some great advice on things I didn’t touch on.
