Power Brake Units - DELCO-Moraine Single Diaphragm: Overhaul: Disassembly

Scribe a mark on bottom of front and rear housings to facilitate reassembly. Mark staked interlocks so they will not be restaked, then straighten staked interlocks. Attach tool J-22805-01 to front of housing, and tool J-9504-01 to rear of housing and turn rear housing counterclockwise to unlocked position. Loosen housing carefully as it is spring loaded.
Lift rear housing and power piston assembly from unit. Remove return spring. Remove retaining ring on push rod then remove silencer. Remove seal, vacuum check valve and grommet from front housing.
NOTE: Care must be taken during the following procedures to prevent damage to diaphragm.
Remove power piston assembly from rear housing. Remove silencer from neck of power piston tube. Remove lock ring from power piston by prying one end out from under large divided locking lug and then pulling ring from under other two locking lugs.
Remove reaction retainer, piston, reaction plate, 3 reaction levers and air valve spring. Remove reaction bumper and air valve spring retainer from air valve.
Place power piston tool J-21524 with square shank in vise. Hold support plate and power piston with tube of power piston up. Pull diaphragm edges away from support plate so a grip can be had on the support plate. Position assembly on tool J-21524 so 3 lugs on tool fit into 3 notches on power piston.
Press down on support plate and rotate counterclockwise until support plate separates from power piston. Remove diaphragm from support plate and set both parts aside.
Drill a 1 3/8" hole in the center of a 2" x 4" x 8" block of wood. Place power piston with tube down in block. Place block in vise and clamp in place. Do not clamp tube.
Remove snap ring on air valve. Place power piston, tube down in a press. Using a 3/8" drive extension, press out air valve assembly. Remove floating control valve, floating valve retainer, push rod limiter washer and air filter.
Remove floating control valve assembly from push rod. Discard control valve as a new one must be installed. Remove master cylinder push rod then remove "O" ring from push rod.