Maxibrake® 50-SERIES
Spring Brakes Service and Parts
Removal
WARNING:
Spring brake chambers are under compressed spring force.
Installation and maintenance should be performed in full accordance with
manufacturer’s written instructions.
1.
Block wheels to prevent vehicle movement when removing brakes. If air is
available, apply to the emergency inlet to release the spring. Remove the plug
at the rear center of the emergency cylinder. Install the release bolt and
washer and turn the bolt until it contacts the internal stop. A sudden increase in
torque will occur when the stop is contacted. Release all air.
2.
If no air is available, remove the plug and install the release bolt and
washer using a hand wrench. Turn the bolt until it contacts the internal stop.
This will compress and hold the emergency springs. At this time, the spring
brake is at “0” stroke and all force is released from the brake adjuster/brake
shoes.
3.
Remove the yoke pin cotter key and yoke pin from the yoke. If attached to
a hydraulic master cylinder, remove the brake from the bracket.
4.
Disconnect the air lines from the brake. Remove the mounting nuts and
washers and remove the spring brake from the mounting. The unit weighs
approximately 50 lbs.
Disassembly
1.
Remove the filter retaining ring and yoke (Fig. 1). Make sure the yoke jam
nut (if applicable) is retained on the push rod. This will aid disassembly.
2.
Apply air to emergency inlet and remove release bolt and washer (Fig. 2).
Release air. If air is not available, remove bolt and washer with a hand wrench
(Fig. 3).
3.
Position the brake in a press (Fig. 4) with a minimum throat opening height
of 25 inches and a minimum stroke of 14 inches. A press plate with 7/8”
mounting holes, 4 3/4” center to center, and a 1 1/2” push rod hole is
necessary for safety and ease of disassembly. Secure the brake in the press
placing the push rod and mounting studs through the press plate.
4.
Apply the press slowly with a light, firm pressure (Fig. 5). Excessive force
could damage the brake unit.
5.
Remove all cap screws from the service and emergency chambers (Fig. 6).
6.
Slowly retract the press (Fig. 7) allowing the springs to expand to their full
free height.
7.
Remove jam nut from service piston (Fig. 8) and remove return spring
locator and spring. Disassemble packing cup by removing self-tapping screws
in packing retainer (Fig 9 and 10). Piston bearing can be removed by splitting
outer surface with chisel (Fig.11).
DO NOT DAMAGE PISTON SURFACE.
Buff
sealing compound and surface residue with wire wheel.
8.
(Packing Cup Emergency Piston)
Disassemble packing cup by removing self-tapping screws in packing retainer
(Fig. 12). Piston bearing can be removed in the same manner as the service
piston (Fig. 13). Buff sealing compound and surface residue with wire wheel.
(O-Ring Emergency Piston)
Remove O-ring seal and split bearing from the piston. Thoroughly clean piston.
9.
Remove snap ring, nylon bushing and O-rings from the bulkhead (Fig. 14).
10.
All non-kit parts should be inspected for excessive wear and repaired or
replaced as needed.
