The master cylinder on the 1977 Pontiac Firebird creates the hydraulic pressure to stop the vehicle. This component has several rubber O-rings and valves that open and close to create the pressure. Over time, the O-rings can weaken, or the valves may simply wear out. When this happens, the brake pedal may feel soft or completely depress before engaging the brakes. No matter the symptom, this is a dangerous condition to drive in and you should replace the master cylinder as soon as possible.
Tools Used: Line wrench set, Combination wrench set, 1 qt. DOT 3 brake fluid, Thread tape, Floor jack, Jack stands, Drain pan, Bench vise with jaw protectors, 1/2-gallon or larger container, Turkey baster, Clean shop rag, Bench bleeding kit, 1 foot of rubber hose,1/4-inch, Assistant
Install the Master Brake Cylinder
Removal
Open the Firebird's hood and open the mater cylinder's cap by pushing the wire retainer to the side and removing the metal lid. Pull the rubber insert from inside the master cylinder.
Siphon out all of the old fluid from inside the master cylinder, using the turkey baster. Transfer this fluid to a 1/2-gallon or larger container to be properly disposed of later.
Place a clean shop rag on the fender well, directly below the brake lines running into the master cylinder, to protect the paint from damage. Loosen and remove the two metal brake lines on the driver's side of the master cylinder, using a brake line wrench. .
Loosen and remove the two nuts and washers holding the master cylinder to the brake booster, the large metal component directly behind the master cylinder, using a combination wrench. Pull the master cylinder, gasket and rubber boot towards the front of the vehicle and off the brake booster.
Bench Bleeding
Place the new master cylinder on in a bench vise with rubber jaw protectors. Tighten the vise until the master cylinder is secured.
Remove the plastic inserts covering the brake line holes on the new master cylinder. Hand-tighten the bench bleeder kit's hoses into the brake line holes and snug the hoses with a brake line wrench.
Fill the master cylinder with new DOT 3 brake fluid and bend the bleeder hoses so the ends are completely submerged in brake fluid.
Press and release, in 3/4- to 1-inch strokes, the plunger on the rear of the master cylinder, using the bleeding tool included with the bleeder kit. Observe as air bubbles come from the bleeder hoses. Repeat this step until no air bubbles come from the hoses.
Loosen the vise and remove the master cylinder.
Installation
Place the new rubber boot inside the brake booster in the same orientation as the old one. Place the master cylinder gasket over the mounting studs on the brake booster.
Mount the master cylinder on the studs protruding from the brake booster; be careful not to spill any brake fluid from the cylinder. Place the washers on the studs and tighten the nuts using a combination wrench.
Place a thin layer of thread tape over the threaded nuts for each brake line. This prevents future leaks, if the nuts are slightly worn out.
Loosen and remove one of the bleeder hoses, using the brake line wrench. Quickly thread in the brake line and tighten it with the brake line wrench. Repeat this step for the other brake line.
Place the rubber insert and lid on the new master cylinder and lock the lid by pulling the metal retainer over the metal lid until it snaps into place. Remove the shop rag from the fender well.
Brake Bleeding
Raise the front of the vehicle, using the floor jack, and secure it with jack stands. Position the stands beneath a frame rail for support. Slowly lower the Firebird until the weight of the vehicle is resting on the jack stands.
Place the drain pan below one wheel. Place the 1/4-inch rubber hose on the brake bleeder valve, the brass valve at the top-rear of the caliper.
Instruct your assistant to pump the brake pedal until it is firm, then hold the pedal. Turn the bleeder valve one-quarter of a turn counterclockwise and observe as fluid and air escapes from the 1/4-inch hose. Repeat this step until only fluid flows from the hose.
Remove the master cylinder lid and check the master cylinder fluid level. Add more fluid if it is below the "Min" line inside the master cylinder. Replace the master cylinder rubber insert and lid, locking it in place with the metal retainer.
Repeat steps 2 through 4 of this section for the wheel on the other side of the Firebird.
Remove the jack stands and lower the vehicle to the ground.
Raise the rear of the vehicle, using the floor jack, and secure it with jack stands. Position the stands beneath a frame rail for support. Slowly lower the Firebird until the weight of the vehicle is resting on the jack stands.
Place the drain pan below one wheel. Place the 1/4-inch rubber hose on the brake bleeder valve, the brass valve at the top-rear of the brake backing plate, the large metal plate behind the rear brakes..
Instruct your assistant to pump the brake pedal until it is firm, then hold the pedal. Turn the bleeder valve one-quarter of a turn counterclockwise and observe as fluid and air escapes from the 1/4-inch hose. Repeat this step until only fluid flows from the hose.
Remove the master cylinder lid and check the master cylinder fluid level. Add more fluid if it is below the "Min" line inside the master cylinder. Replace the master cylinder rubber insert and lid, locking it in place with the metal retainer.
Repeat steps 7 through 8 of this section for the wheel on the other side of the Firebird.
Remove the jack stands and lower the Firebird to the ground.
Open the master cylinder lid and remove the rubber insert. Check the fluid level relative to the "Max" and "Min" lines inside the caliper. Add or remove DOT3 fluid so it is between the two lines.
Pour all of the old brake fluid into the 1/2-gallon container and dispose of it properly. Most auto-parts stores will dispose of old fluids free of charge.
Tips & Warnings
This process is only valid for Firebirds with power brakes.
Bench bleeding and brake bleeding are required when performing this task.
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