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Overhaul



POWERMASTER OVERHAUL

IMPORTANT: Refer to Technical Service Bulletins for the latest information.

IMPORTANT: Some components of the Powermaster system appear to be similar to the Antilock Braking System (ABS) but they are different. Powermaster System is not an antilock braking system.

DISASSEMBLY

WARNING: Failure to fully depressurize Powermaster unit before performing service operations could result in injury to service personnel and damage to painted surfaces.

Exploded View Of Powermaster Assembly:





1. Depressurize Powermaster by turning ignition off, applying and releasing brake pedal a minimum of 10 times using approximately 50 pounds force on the pedal.
2. Remove reservoir cover and diaphragm (32). Empty fluid from reservoir (33).

Figure 2 Pressure Switch:





3. If installed:
a. Remove pressure switch (1) and O-ring (2).

Figure 3 Accumulator:





b. Remove accumulator (3) and O-ring (4).

Figure 4 E-H Pump And Pressure Hose:





c. Remove Electro-Hydraulic (E-H) pump (8) and pressure hose assembly (11).

Figure 5 Sump Hose, Tube Nut & Assembly, and Motor and Pump Brackets:





d. Remove sump hose (9), clamps (10), tube and nut assembly (12), and brackets (14 and 15).

CAUTION: Use care not to scratch or otherwise damage outside diameter sealing surface at pushrod end of power piston assembly (25) and bores in Powermaster body (39). These are primary sealing surfaces for this unit.

4. Remove retainer (18) from groove in Powermaster body (39).
5. Remove boot, retainer, pushrod, power piston group (16 thru 25) by grasping and pulling pushrod.
6. Remove retainer (16) and boot, pushrod, socket group (17) and piston guide (19) from power piston assembly (25).
7. Remove O-ring (20) from piston guide (19) and O-rings (21) from power piston assembly (25) and piston guide (19).
8. Remove reaction body group (22) from power piston assembly.
9. Remove reaction piston (23) and reaction disc (24) from reaction body group (22).

CAUTION: Do not attempt further disassembly of reaction body group (22) or power piston assembly (25). If damage is noted or fault isolated to reaction body group or power piston assembly, they shall be replaced as assemblies.

10. Remove primary piston assembly (26) and secondary piston assembly (27 thru 30) by directing a small amount of compressed air into outlet port at blind end of body, other outlet port plugged.
11. Remove secondary seal (27), spring retainer (28) and primary seal (29) from secondary piston (30).
12. Remove spring (31) from body bore.

Figure 8 Removing Reservoir:





13. Install Powermaster body in vise.

CAUTION: Do not clamp across Powermaster body.

14. Remove reservoir (33) using pry bar (45).
15. Remove reservoir grommets (34 and 35).
16. Remove valve seat and seal (36) and discard.

NOTE: To remove valve seat tap "easy out" into seat and pull straight out.

17. Remove poppet (37) and spring (38) and discard.

CAUTION: Do not immerse pressure switch (1) or E-H pump (8) in alcohol. Exterior surfaces may be wiped with a clean cloth lightly moistened with denatured alcohol if necessary.

Exploded View Of Powermaster Assembly:





CLEANING AND INSPECTION:
- Clean all parts except pressure switch (1) and E-H pump (8) in clean, denatured alcohol.
- Dry with filtered compressed air.
- Inspect all metal parts for cracks, distortion or other evidence of structural damage.
- Inspect primary sealing surfaces on power piston (25) for scoring, deep scratches or other damage that would cause leakage. if noted replace power piston assembly.
- Inspect power piston and master cylinder bores in Powermaster body for scoring or corrosion. If noted, replace power brake assembly. No abrasives shall be used.

NOTE:
^ Use clean, fresh brake fluid to lubricate parts prior to assembly.
^ Lubricate new rubber O-rings, grommets and seals with clean brake fluid just prior to assembly.
^ Lubricate master cylinder and power piston bores in Powermaster body before installing parts.

ASSEMBLY
1. Install Powermaster body (39) in vise.
2. Install new spring (38) and poppet (37) in Powermaster body (39).
3. Install new valve seat and seal (36) in Powermaster body (39).
4. Bottom out valve seat and seal (36) by threading nut of tube and nut assembly (12) into Powermaster body port.
5. Remove Powermaster body (39) from vise.
6. Install grommets (34 and 35) into Powermaster body (39).

CAUTION: Make sure grommets are properly seated.

Figure 9 Installing Reservoir:





7. Install reservoir (33) to Powermaster body (39).
8. Install spring (31) in Powermaster body (39).
9. Install secondary seal (27), primary seal (29) and spring retainer (28) on secondary piston (30).
10. Install secondary piston assembly (27 thru 30) in Powermaster body (39).
11. Install primary piston assembly (26) in Powermaster body (39).
12. Install reaction piston (23) and new reaction disc (23) in reaction body group (22).
13. Install two O-rings (21) on power piston assembly (25).
14. Install reaction body group (22) in power piston assembly (25).
15. Install power piston assembly (25) in Powermaster body (42).
16. Install one O-ring (21) on piston guide (19); O-ring (20) in piston guide.
17. Install piston guide (19) in Powermaster body (39), over power piston (23).
18. Install retainer (18) while depressing piston guide (19) and power piston (25).
19. Install boot, pushrod, socket group (17), socket into end of power piston assembly (25) and retained with retainer (16).
20. Assemble external components:

Figure 5 Sump Hose, Tube Nut & Assembly, and Motor and Pump Brackets:





a. Install brackets (14 and 15) with bolts (13) and torque to 20-34 Nm (15-25 lb. ft.).
b. Install sump hose (10), clamps (9), tube and nut assembly (12). Torque tube and nut assembly to 13-20 Nm (10-15 lb. ft.).

Figure 4 E-H Pump And Pressure Hose:





c. Install E-H pump (8), washers (6) and attaching nuts (5) and torque to 2.6-4.0 Nm (23-35 lb. in.).
d. Install pressure hose assembly (11).
- First connect end of hose assembly (11) to E-H pump (8) and torque to 13-20 Nm (10-15 lb. ft.).
- Connect other end of pressure hose assembly (11) to tube and nut assembly (12) and torque to 13-20 Nm (10-15 lb. ft.).
e. Install end of sump hose (10) and hose clamp (9) to E-H pump (8).

Figure 3 Accumulator:





f. Install O-ring on accumulator (3) then torque accumulator (4) to 20-27 Nm (15-20 lb. ft.)

Figure 2 Pressure Switch:





g. Install O-ring (2) on pressure switch (1) and torque pressure switch to 20-27 Nm (15-20 lb. ft.)

21. Install reservoir cover and diaphragm (32) on reservoir (33).
22. Install Powermaster assembly in vehicle.
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