1991 Pontiac Firebird Brake Service (ONLINE REPAIR MANUALS)

• Lubricate parking brake lever fulcrum with suitable brake lube, then attach lever to brake shoe. Ensure lever operates smoothly.
• Connect brake shoes with adjusting screw spring, then position adjusting screw.Ensure adjusting screw star wheel does not contact adjusting screw spring after installation and also ensure righthand thread adjusting screw is installed on left side of vehicle and lefthand thread adjusting screw is installed on right side of vehicle. When brake shoe installation is completed, ensure starwheel lines up with adjusting hole in backing plate.
• Lightly lubricate bac...

• Raise and support rear of vehicle, then remove tire and wheel assembly.
• Remove brake drum. If brake lining is dragging on brake drum, back off brake adjustment by rotating adjustment screw. Refer to individual car chapter for procedure.If brake drum is rusted or corroded to axle flange and cannot be removed, lightly tap axle flange to drum mounting surface with a suitable hammer.
• Using brake spring pliers or equivalent, unhook primary and secondary return springs,Figs. and . Observe location of brake parts being removed to aid during installation.
• Remove brake hold-down springs with suitab...

These brakes have self-adjusting shoe mechanisms that assure correct lining-to-drum clearances at all times. The automatic adjusters operate only when the brakes are applied as the car is moving rearward.

Although the brakes are self-adjusting, an initial adjustment is necessary after the brake shoes have been relined or replaced, or when the length of the adjusting screw has been changed during some other service operation.

Frequent usage of an automatic transmission forward range to halt reverse vehicle motion may prevent the automatic adjusters from functioning, thereby induc...

BRAKE DRUMS

Any time the brake drums are removed for brake service, the braking surface diameter should be checked with a suitable brake drum micrometer at several points to determine if they are within the safe oversize limit stamped on the brake drum outer surface. If the braking surface diameter exceeds specifications, the drum must be replaced. If the braking surface diameter is within specifications, drums should be cleaned and inspected for cracks, scores, deep grooves, taper, out of round and heat spotting. If drums are cracked or heat spotted, they must be replaced. Mi...

BRAKE SHOE & LINING REMOVAL

• Remove^2/3 of the total brake fluid capacity from master cylinder reservoir.
• Raise and support vehicle, then remove tire and wheel assembly.
• Install two wheel retaining nuts to retain rotor in position.
• Position one end of a suitable C-clamp against inlet fitting bolt, and the other end against outboard shoe and lining, then tighten clamp as shown, Fig. , until piston fully bottoms in caliper bore.
• Remove upper guide pin bolt and discard.
• Loosen lower guide pin bolt, then pivot caliper downward on the lower guide pin bolt to expose the shoe & lining assemblies. Use ...

DESCRIPTION

This power brake unit is a suspended type vacuum brake booster which utilizes engine intake manifold vacuum and atmospheric pressure to assist in braking,Fig. .

The unit consists of a vacuum power section and a hydraulic master cylinder section. The vacuum power section contains a power piston with rolling diaphragm mechanism and power piston return spring.

The control valve consists of an air valve and floating vacuum control valve assembly. The reaction mechanism consists of a hydraulic piston, reaction plate and a series of levers. The valve opera...