The brake booster provides power assistance during braking. Inside there is a disc-like diaphragm that separates the booster’s two halves. When the engine is running, vacuum is applied to both sides of the booster. When the driver steps on the brakes, the pedal operates a valve which allows outside air to enter. This allows atmospheric pressure to enter the booster, creating a pressure differential that forces the booster power forward into the master cylinder for power assist. When the brakes are released, vacuum returns to both sides of the booster and a spring returns the diaphragm to its original position.
If the power brake booster is not functioning properly, you will notice problems such as the brake pedal being very hard to press, and the vehicle taking longer than normal to come to a stop. It may be time to replace the power brake booster.
- Protective gloves
- Ratchet, sockets and extension
- Repair manuals (optional)
- Replacement brake booster
- Safety glasses
- Screwdriver and/or small pick
Part 1 of 2: Remove the faulty brake booster
Step 1: Locate the brake booster. The brake booster will be mounted to the firewall on the driver’s side.
Step 2: Remove the master cylinder from the brake booster. Remove the master cylinder fasteners using a ratchet or wrench. Then pull the master cylinder away from the booster. Typically, the brake lines are long enough that this can be done without disconnecting the lines.
Step 3: Disconnect the booster vacuum supply line. Remove the hose clamp by squeezing it with a pair of pliers and sliding it away from the booster. Then gently remove the hose by pulling it away from the booster.
Step 4: Disconnect the booster pushrod from the brake pedal. Using a small screwdriver or pick, remove the retaining clip from the booster pushrod. Then remove the pushrod from the brake pedal.
Step 5: Remove the brake booster fasteners. Remove the fasteners securing the booster to the bulkhead. These are typically located under the dashboard. The best way to reach them is by using a ratchet with an extension.
Step 6: Remove the brake booster. Pull the booster away from the firewall and remove it from the vehicle.
Part 2 of 2: Install the new brake booster
Step 1: Position the new brake booster unit. Place the new brake booster in the same location that the old one was removed from.
Step 2: Reinstall the fasteners. Reinstall the brake booster fasteners and tighten them down using a ratchet and extension.
Step 3: Reconnect the pushrod to the brake pedal. Reinstall the pushrod onto the brake pedal and put the clip back on.
Step 4: Reconnect the booster vacuum hose. Slide the vacuum hose back onto the booster. Then reinstall the hose clamp by squeezing it with a pair of pliers and sliding it onto the booster.
Step 5: Reinstall the master cylinder. Reinstall the master cylinder and tighten down the mounting bolts using a ratchet or wrench.
Replacing a brake booster can be tough. If this seems like something you’d rather leave to the professionals, YourMechanic offers expert brake booster replacement conveniently done at the time and place of your choice.
This article originally appeared on YourMechanic.com as How to Replace a Power Brake Booster.
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