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Brake Booster Replacement
 
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Pelican Technical Article:

Brake Booster Replacement

Steve Vernon

Time:

4-8 hours

Tab:

$250 to $700

Talent:

****

Tools:

13mm deep socket, 11mm flare-nut wrench, pliers

Applicable Models:

Porsche 944 (1983-89)
Porsche 944 S2 (1989-91)
Porsche 944 Turbo (1986-89)
Porsche 944S (1987-88)

Parts Required:

Booster, brake fluid

Hot Tip:

Watch for spills

Performance Gain:

Better braking performance

Complementary Modification:

Check your brake pads

Your brakes are the most important systems on the car, period. The brake booster helps ease the amount of foot pressure you need to apply the brakes. If you are starting to feel you are using more or uneven pressure the booster may be starting to go. Replacing the booster on the Porsche 944 is not difficult. It is just a tight fit, but replacing the booster on the 951 is another story. While people have told me of "friends" who replaced the booster without removing the heat shield for the turbo, I have never seen it done. Changing the booster on a 944 should take around 4 hours including bleeding the brakes, while a 951 could easily run into 5-8 hours.

You are going to be working with brake fluid. An important thing to remember is that brake fluid is toxic to humans and paint. Brake fluid spilled on paint will permanently mar the surface, so be very careful not to touch the car if you have it on your hands and clothing. If you do get a spot on your paint, make sure that you blot it with a paper towel. Don't wipe or smear it. Then quickly rinse it with plenty of water. It's also important not to try to clean it off with any chemical or other cleaning solutions. Always make sure you catch and dispose of the fluid in accordance with the regulations in your area.

When completed you must properly bleed the entire brake and clutch system! Do NOT attempt to drive the vehicle until you have properly bled the system.

There is a heat shield on the Porsche 951 that protects the brakes from the heat of the turbo (red arrow).
Figure 1

There is a heat shield on the Porsche 951 that protects the brakes from the heat of the turbo (red arrow). You will need to remove this shield to replace the booster. Please see our article on brake heat shield removal for additional assistance.

Before removing the booster you will need to remove the master cylinder and reservoir.
Figure 2

Before removing the booster you will need to remove the master cylinder and reservoir. Please see our article on master cylinder and reservoir removal for further information and perform that work first.

You are going to be working inside the vehicle around the pedal cluster.
Figure 3

You are going to be working inside the vehicle around the pedal cluster. It is a really tight fit under the dash. I like to remove both the steering wheel and the front driver's seat to give myself more room. If you need or want more room to work please see our articles on seat and steering wheel removal for instructions on how to remove them. The brake booster shaft (red arrow) is held in place on the brake pedal by a clip (yellow arrow). Use a set of pliers and remove the clip from the pin and wiggle the pin out. This will free the booster shaft from the brake pedal.

There are three 13mm nuts (red arrows) located behind the sound proofing that holds the booster to the firewall.
Figure 4

There are three 13mm nuts (red arrows) located behind the sound proofing that holds the booster to the firewall. Fold the carpet foam back and remove the nuts. This is the time when you will wish you had removed the seat and steering wheel if you haven't.

Move to the engine area and disconnect the check valve hose from the booster (red arrow).
Figure 5

Move to the engine area and disconnect the check valve hose from the booster (red arrow).

You can now easily remove the booster.
Figure 6

You can now easily remove the booster.

You will need to use a 13mm deep socket and remove the four bolts holding the intermediate plate to the booster and transfer it to the new booster.
Figure 7

You will need to use a 13mm deep socket and remove the four bolts holding the intermediate plate to the booster and transfer it to the new booster. Note the orientation (yellow arrow) of the mount. Make sure to install it in the correct position for the check valve.

Now is a really good time to clean up the area around the steering shaft that is usually covered in dirt, grim and spilled brake fluid (yellow arrow).
Figure 8

Now is a really good time to clean up the area around the steering shaft that is usually covered in dirt, grim and spilled brake fluid (yellow arrow). If you have had any issues with the clutch master cylinder or it is just old this is the perfect time to replace it. You have easy access to it, and you are going to have to bleed the system any way (red arrow).

Before installing the booster make sure to transfer over the pedal bracket and leave the securing nut loose until the installation is complete (red arrow).
Figure 9

Before installing the booster make sure to transfer over the pedal bracket and leave the securing nut loose until the installation is complete (red arrow).

The rest of the installation is the reverse of removal.
Figure 10

The rest of the installation is the reverse of removal. You will now need to completely bleed the brake and clutch system. Please see our article on how to bleed your brakes and clutch slave cylinder bleeding for further assistance. Do NOT attempt to drive the vehicle until you have properly bled the system.


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