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Home >> Pontiac >> 1971 >> GTO Base, 7.5L Eng, Eng CD WC, Not Available Trans >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Power Brake Units - DELCO-Moraine Single Diaphragm >> Overhaul >> Reassembly

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

  1. NOTE: Lubricate all rubber parts, plastic and metal friction points with suitable lubricant (Delco Silicone Lube #5459912), prior to installation.

    Replace check valve (with new grommet), if removed during disassembly. Install new front seal. Install new "O" ring in groove on master cylinder piston rod, then insert rod through reaction retainer, with round end at tube end of retainer. Place suitable support plate tool (J-21524) in vise and position power piston on tool. Install new "O" ring on NEW (if removed) air valve assembly, in second groove from push rod forward end. Press NEW air valve assembly, into seat in power piston tube. Install new valve retainer and press into place with suitable tool (J-21601). Install push rod limiter washer (except Chevelle) over push rod, then install air filter. Press raised flange of power piston diaphragm through center hole of support plate. Hold steel support plate (not diaphragm), place over power piston tube, seating diaphragm flange in groove of tube.

  2. Place assembly in padded vise (tube down). DO NOT clamp. Install snap ring in air valve groove. Seat the air valve spring on snap ring and reaction bumper in groove in end of air valve. Position air valve return springs and reaction levers in place. Set reaction plate (numbered side up) on levers and press down until levers pop into place. Assemble master cylinder rod and reaction retainer to power piston. Secure assembly with lock ring on power piston. Install air filter on push rod.
    Fig 1: Delco-Moraine Single Diaphragm Power Unit
    G09333049Courtesy of GENERAL MOTORS COMPANY
  3. Install new seal in center of rear housing. Assemble power piston to rear housing. Place felt silencer and retainer clip on push rod. Install push rod boot to power piston tube. Assemble lock nut and clevis (if equipped) to push rod. Place front housing assembly on suitable holding fixture (J-22805). Place power piston return spring in front housing. Position rear housing to front housing and lock together.
    NOTE: If housings do not easily lock together, apply vacuum to check valve.
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