1979 Delta Master Cylinder Removal

The 1918 addition of hydraulic power to the braking system forever changed the way cars stopped. No longer did vehicles require an extravagant series of pulleys and levers to bring them to a stop; instead, hydraulic fluid took the place of these old mechanical systems. The 1979 Oldsmobile Delta 88 added a little extra innovation to Lougheeds hydraulic braking system: It used the engine's vacuum to magnify the drivers foot pressure on the brake pedal, by way of a brake booster. The Deltas master cylinder, the heart of the hydraulic brake system, mounts directly to the brake booster, making its replacement straightforward. After replacing the master cylinder, you must bleed the air from the brake system.

Instructions

Removing and Replacing

1

Press the metal locking wire on the master cylinder aside to unlock the lid. Pull the metal lid off the master cylinder, then pull off the rubber diaphragm under the cap. Siphon out as much of the fluid from the master cylinder as possible with a turkey baster. Transfer this siphoned fluid to a small, sealable container and seal the container.

2

Hold a small drain pan under the master cylinder and loosen the brake line fitting with a line wrench. Pull the brake lines from the master cylinder and allow the fluid to drain into the small drain pan. Pull the drain pan from under the master cylinder when the fluid stops draining. Immediately wrap the end of each brake line with a clean, lint-free cloth to prevent debris from entering the system.

3

Remove the master cylinder-retaining nuts with a ratchet and socket, and pull the master cylinder from the brake booster.

4

Set the new master cylinder in a bench vise fitted with rubber jaw protectors. Tighten the bench vise until it holds the master cylinder in place; do not tighten the vise too much, as it can potentially crack the master cylinder.

5

Remove the two plastic caps inserted in the brake line ports of the new master cylinder. Hand-thread the bleeder lines included in the master cylinder bleeder kit into the brake line ports. Snug the bleeder lines with a line wrench.

6

Fill the new master cylinders reservoir to the Max line with fresh DOT 3 brake fluid. Bend the bleeder lines upward and submerge their ends into the DOT 3 brake fluid in the master cylinder reservoir.

7

Press and release the plunger on the rear of the master cylinder with a wooden dowel rod. Watch the ends of the bleeder lines in the brake fluid and look for air bubbles coming from them. Continue pressing and releasing the plunger until no fluid comes from the ends of the hoses.

8

Remove the bleeder lines from the master cylinder with a line wrench and immediately press the plastic caps back into the brake line ports.

9

Install the new master cylinder on the mounting studs on the brake booster. Hand-tighten the master cylinders retaining nuts onto the studs. Torque these retaining nuts to 22 to 30 foot-pounds with a torque wrench and socket.

10

Pull the plastic caps from the brake line ports. Unwrap the clean, lint-free cloths off the ends of the brake lines and insert the brake lines into the brake line ports on the master cylinder. Hand-thread the brake line fittings into the brake line ports, then torque the fittings to between 10 and 13 foot-pounds with a torque wrench and a crows foot attachment.

11

Add DOT 3 brake fluid to the master cylinder until the fluid level reaches the Max line on the reservoir. Proceed to the section titled Bleeding the Brakes.

Bleeding the Brakes

12

Raise the front of the Delta with a floor jack and position jack stands under its frame rails. Lower the front of the Oldsmobile onto the jack stands. Raise the rear of the vehicle with a floor jack and slide jack stands under the rear part of the frame rails. Lower the vehicle onto the jack stands.

13

Crawl under the rear of the Delta, so that you are right behind the right rear wheel. Find the brake bleeder valve -- the -inch metal valve -- on the top of the drum brake backing plate. Press one end of a -inch-diameter rubber hose onto the bleeder valve and set the other end in a clean, clear container. Fill this container with new DOT 3 brake fluid until the fluid submerges the end of the hose.

14

Instruct an assistant to press and release the brake pedal until the pedal feels firm -- about five to seven strokes-- then tell your assistant to hold the pedal to the floor. Turn the bleeder valve a half-turn with a combination wrench and inspect the end of the hose in the small container to determine whether air bubbles are coming from the hose. Tighten the bleeder valve and instruct your assistant to release the brake pedal. Repeat this step until air bubbles stop coming from the end of the hose.

15

Remove the rubber hose from the bleeder valve. Refill the brake master cylinder to the Max line.

16

Repeat steps 2 through 4 to bleed the remaining three wheels, in the following order: left rear, right front, then left front. When bleeding the front brakes, the bleeder valve is on top of the caliper, as opposed to the drum brake backing plate.

17

Raise the rear of the Delta off the jack stands with a floor jack and remove the jack stands. Lower the rear of the vehicle to the ground. Raise the front of the Delta off the jack stands with a floor jack and remove the jack stands. Lower the front of the Delta to the ground.

18

Insert the rubber diaphragm into the master cylinder and set the metal lid on top of the master cylinder. Pull the metal locking wire upward and press it over the lid until it seats into the groove on the lid.

19

Take the old brake fluid to a local used automotive fluid recycling center. Some auto parts stores take this fluid free of charge.