Operation and maintenance manual

Section 170-0030
Parking Brake - Actuator
SM 2166 Rev 1 10-03
2
4. Release spring tension on clevis pin (7) by
unscrewing tensioning bolt on slack adjuster (3) until
clevis pin (7) feels loose. Remove cotter pin (8) and
clevis pin (7) from actuator (9).
Note: On engine shutdown the parking brake will
automatically apply. Ensure there is sufficient
clearance for actuator rod travel.
5. Switch off the engine and place the battery master
switch in the 'Off' position.
6. Disconnect and plug hydraulic line from actuator (9).
Cap actuator (9) and hydraulic line to prevent entry of
dirt.
7. Remove nuts (10) and washers (11) securing actuator
(9) to cap assembly (13). Remove actuator (9) from cap
assembly (13) and set aside for disassembly.
REPLACEMENT OF SEALING RINGS
Numbers in parentheses refer to Fig. 2.
Note: Before and during assembly and disassembly of
the brake actuator precautions should be taken to
avoid damaging plunger (12) assembly.
Disassembly
1. Turn bolt (34) until it is approximately 25 mm (1 in)
out of cap (31).
2. Remove bolts (30) from the periphery of actuator
housing (1).
3. Press cap (31) approximately 10 mm (0.4 in) into
actuator housing (1). If necessary use a rubber
hammer.
4. Remove retaining ring (39) from the boss of actuator
housing (1).
5. Press plunger (12) fully in. Cap (31) with springs (37
& 38) will be pressed out of actuator housing (1).
WARNING
Springs (37 & 38) have been assembled under
pressure. Bolts (24 & 34) should not be turned
in this situation.
6. Turn joining nipple (21) and remove from actuator
housing (1). Remove and discard U-sit ring (19) and
grommet (20).
7. Remove four bolts (6) and lockwashers (5) from the
front cap.
8. Remove the hydraulic unit, with plungers (12 & 23)
and base (22), from actuator housing (1).
9. Press plungers (12 & 23) out of base (22).
10. Remove and discard wiper (13), U-cups (15 & 28)
and 'O' ring (16) from hydraulic unit.
11. Carefully press plunger (12) assembly out of
plunger (23). Remove and discard 'O' ring (17) from
plunger (23).
Note: Remove 'O' rings carefully from 'O' ring grooves
in order to avoid damaging the grooves.
Assembly
1. Install new 'O' ring (17) in plunger (23) and carefully
press plunger (12) assembly into plunger (23).
2. Install new wiper (13), U-cups (15 & 28) and 'O' ring
(16) in/on hydraulic unit, as shown in Fig. 2.
Note: U-cups (15 & 28) close, but only in one direction.
These should be assembled with the groove side in the
correct direction, as shown in Fig. 2.
3. Lightly grease plunger assembly (12 & 23) and
install in base (22). Install 'O' ring gland (14) in base (22).
4. Install the hydraulic unit with Tectyl 280 rust preventive
or equivalent, against the front cap in actuator housing (1).
Secure hydraulic unit to the front cap with four bolts (6) and
lockwashers (5). Tighten bolts (6) to a torque of 25 Nm (18
lbf ft).
5. Grease new grommet (20) and install in actuator
housing (1).
6. Install new U-sit ring (19) on joining nipple (21).
Smear the threads of joining nipple (21) with
Loctite 270 and install through grommet (20). Tighten
joining nipple (21) to a torque of 95 Nm (70 lbf ft).
7. Install rear cap (31) assembly, complete with springs
(37 & 38), in actuator housing (1).
8. Press rear cap (31) assembly approximately
10 mm (0.4 in) under the rim of actuator housing (1).
9. Smear groove in actuator housing (1) and retaining
ring (7) with Tectyl 280 or equivalent, and install
retaining ring (7) in the groove.