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

  1. Scribe a line across front and rear housing for reassembly. Remove vacuum valve and grommet from front housing and discard.
  2. Position housing unlock tool (J-23456) in a vise. Mount diaphragm unit in tool so that 4 studs on unit fit in holes provided in tool. Straighten staked interlocks.
  3. Position spanner wrench over two studs with tubular portion of wrench that fits over the studs down. Rotate screw on unlock tool to apply downward pressure to housing. Turn handle counterclockwise to unlock housing. Turn screw to release tension and remove front housing.
  4. Remove tools from housings. Remove power piston return spring. Remove boot and boot retainer from the rear housing and push rod. Remove felt silencer from inside the boot. Remove power piston assembly. Remove power piston bearing from center opening in rear housing.
  5. Remove reaction retainer and piston rod from power piston. Remove silencer from neck of piston tube. Turn power piston upside down so end of push rod is against a hard surface. Use a slight force or impact on push rod to remove diaphragm retainer.
  6. Remove diaphragms, support plates and divider from power piston. Remove center bearing from housing divider. Separate primary and secondary diaphragms from support plate.
  7. Remove reaction body retainer using a screwdriver. Remove reaction body. Using a small dowel, push down on the end of reaction piston and remove reaction disc and piston from reaction body.
  8. Remove air valve spring. Remove rubber reaction bumper from end of air valve. Remove retaining ring from air valve. Remove air filter from tube portion of power piston.
    NOTE: If air valve push rod has a formed eye on the end, it cannot be serviced and must be replaced as an assembly.
  9. Remove air valve push rod assembly from push rod end of power piston by pressing out using an arbor press. Use a mandrel no larger than 1/2" diameter.
    NOTE: The push rod can be removed by inserting a heavy shanked screwdriver on both sides of push rod and pulling straight out. A considerable amount of force will be required.
  10. With air valve push rod removed, control valve retainer can be removed. Remove "O" ring from air valve.
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