Genuine Mazda 929 Brake Booster

Mazda 929 Brake Booster Parts and Q&A

• Brake Booster
  HE21-43-800A
  Q: How can the brake booster be rebuilt and what tools are necessary for the process on Mazda 929?

  A:

  The booster can be rebuilt, although several special tools are necessary, and it is advisable to have rebuilding done by an outside repair facility. Begin by removing the master cylinder and disconnecting the vacuum hose from the booster, noting the direction of the arrow on the hose or valve, which should always point toward the engine. Inside the car, disconnect the push rod fork from the brake pedal by removing the clevis pin, then unfasten the attaching nuts to remove the booster and gasket. Install the new gasket with the brake booster and tighten the attaching nuts, then connect the brake pedal linkage to the push rod fork, greasing the clevis pin. Reconnect the vacuum hose in the correct direction and install the master cylinder, followed by bleeding the system. For pushrod clearance adjustments after rebuilding master cylinders on 1983-89 models, a special tool is required since the clearance cannot be measured when assembled. For 1983-85 models, use Mazda tool no. 49-B002-765 or equivalent, and for 1986-89 models, use Mazda tool no. 49-F043-001 or equivalent, along with a vacuum pump for the latter. For 1983-85 models, set the unit on the master cylinder with the adjusting bolt head upward, ensuring both legs rest on the mounting flange, then turn the bolt until it just touches the pushrod recess in the piston. Turn the unit upside down, rest the legs on the power brake unit's mounting flange, and if there is any gap between the pushrod, loosen the locknut and adjust the pushrod until it just touches the bolt head, tightening the locknut afterward to achieve the specified clearance. For 1986-89 models, follow a similar initial setup, then disconnect the vacuum hose from the power brake unit and connect a vacuum source, applying 19.7 in. Hg (66.5 KPa) of vacuum. Turn the unit upside down, check the clearance between the gauge and the pushrod, and adjust the pushrod until all clearance is removed.