TRUCK SERVICE MANUAL
4. Remove screw (28) from body (1).
secure in place with snap ring (7).
5. Remove piston assembly (18) and spring (16)
6. Apply light lubricant to inside bores of body.
Install piston assembly in body.
6. Remove snap ring (7), spring guide (8), spring
7. Install screw (28) with head of screw tight
(12), and shim washers (15).
7. Remove spring (16).
8. Install plunger (6) in mounting plate (2), position
mounting plate on body and secure in place with
8. Remove "O"-ring (17) and vee-block seal (14).
three lock washers (3) and cap screws(4).
9. Remove cap screws (22), lock washers (21),
end cap (24) and gasket (27).
9. Install boot (5) in grooves in mounting plate.
10. Remove cage assembly and "O"-ring (20) from
NOTE: The gap between the exhaust
11. Hold exhaust valve (10), unscrew nut (26) and
valve and seat must be .06" minimum.
remove exhaust valve spring (23) and inlet valve
This may be checked by inserting a
(25) from cage assembly.
feeler gauge through a delivery port.
12. Remove snap ring (13), cap (10), air cleaner (9)
and screen (10A).
Inspection and Cleaning
Plug all cylinder ports. Connect air supply and air
gauge to inlet port. Check exhaust port with soapy
1. Wash all metal parts in mineral spirits or
water. No leakage allowed.
2. Scrape old gasket material from mating surfaces
of end cap (24) and cage assembly.
Connect air supply and air gauge to one cylinder
port. Depress treadle or piston to allow 5 to 10 psi air
3. Clean and wipe dry inlet valve (25) and exhaust
pressure to register on gauge in cylinder port. Check
valve (19). They must be replaced if nicked or
exhaust port with soapy water; a one inch soap bubble in
three seconds permissible.
4. Examine inlet valve seat in cage assembly and
exhaust valve seat on piston (18). They must be
Depress plunger of brake valve slowly so that brake
free of nicks. Crocus cloth may be used to
valve piston movement is also slight. Note that pressure
smooth off slight nicks; if nicks are too deep,
gauge reading at cylinder port builds up in proportion to
replace piston or cage.
pressure gauge reading at inlet port. (The pressure
reading at cylinder port should become greater as
5. Replace boot if cracked or deteriorated.
plunger is further depressed.) With plunger fully
depressed, both gauges should read alike.
plunger is depressed in this holding position, a one inch
1. Place spring (23) on stem of exhaust valve (19)
soap bubble in three seconds at exhaust port is
and install in cage with inlet valve (25) and nut
(26). Tighten securely.
2. Install new "O"-ring (20) in body (1).
Coat the entire valve with soapy water especially
around gaskets, assembly screws, and tubing fittings.
3. Use scratch marks to position gasket (27) and
With brakes released or applied, no leaks are permitted.
cage assembly, install lock washers (21), cap
If tightening the assembly screws or fittings does not
screws (22) and tighten securely.
eliminate air loss, the brake valve must be disassembled
4. Install new "O"-ring (17) and vee-block (14) on
and reassembled correctly.
5. Install shim washers (15) in piston (four normally
When tests determine that brake valve is
required) spring (12) shim washers (11) (two
satisfactory, remove test gauges and air lines from valve.
normally required) and
Prevent the entrance of dirt in valve by plugging all ports
until valve can be reinstalled in air system.