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Power Brake Units - BENDIX Dual Diaphragm: Overhaul: Disassembly

  1. Scribe a mark across front and rear housings for reassembly. Remove master cylinder push rod. Remove both seals from rod.
  2. Remove vacuum check valve and grommet. Remove dust boot and silencer from operating valve rod.
  3. Using an awl, remove dust guard retainer, dust guard and silencers from rear plate. Reinstall steel retainer on hub.
  4. Squirt denatured alcohol down valve operating rod. This will lubricate rubber grommet in valve plunger.
  5. Position 2 small blocks of wood on either side of air valve rod and install end of air valve rod in a vise. Leave just enough room to position 2 open end wrenches between vise and retainer on hub of rear plate.
    Fig 1: Exploded View of Bendix Dual Diaphragm Unit
    G09317437Courtesy of NOT AVAILABLE
  6. Using wrench closest to vise as a pry, force air valve off ball end of rod. Care must be taken not to damage plastic hub or allow vacuum cylinder to fall out.
  7. Of the 12 lances at the rear of the housing 4 are deeper than the rest. These must be straightened so that they will clear cutouts in front housing.
    NOTE: If the metal breaks while being straightened, the housing must be replaced.
  8. Remove push rod and vacuum seal from front housing. Attach a suitable holding fixture (J-22805) to front housing studs. Make sure nuts and washers are tight.
  9. Place unit and holding fixture in arbor press with rear unit up. Place a 1 1/2" wrench on holding fixture and allow wrench to contact rear of arbor press to prevent unit from turning. See Fig 2.
  10. Using a suitable spanner wrench (J-9504) over studs on rear unit. Bolt wrench to studs. Place a piece of pipe (2" I.D., 3" long) over plastic diaphragm plate hub.
  11. Place a piece of flat stock over pipe. Using arbor press, press down on pipe enough to relieve tension of diaphragm rubber lip and spring.
  12. Rotate spanner wrench counterclockwise until lances in edge of rear housing are aligned with cutouts in front housing. Considerable effort may be required.
    CAUTION: The return spring is compressed in power section and expands as housings are separated. If the housings will not separate, tap housings with a rubber hammer to break seal.
  13. After housings are separated, slowly release press until spring tension has been released. Remove front housing and return spring.
  14. Remove spanner wrench and holding fixture. Work edges of front diaphragm from under lances of rear housing. Remove vacuum assembly from rear housing. Care must be taken not to damage rear housing seal.
  15. Wet rear diaphragm retainer with denatured alcohol. Remove retainer with fingers. Place a suitable holding mandrel (J-22839) in a vise. Place the diaphragm and plate on tool with tool seated in front plate hex opening.
  16. Turn rear diaphragm plate counterclockwise. After both plates have been loosened, remove plates from tool. Place on a bench with front plate down. Unscrew and remove rear plate from front plate. Retain air valve plunger and valve return spring as plates are separated.
  17. Remove square ring seal from shoulder of front diaphragm plate hub. Remove reaction disc from inside front diaphragm plate hub.
  18. Carefully remove center plate from hub of front plate. Remove diaphragms from plate. Use a punch or a 1 1/4" socket to drive seal from rear housings.
    Fig 2: Using Arbor Press and Suitable Tools to Separate Unit
    G09317438Courtesy of NOT AVAILABLE
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