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Brake Master Cylinder Replacement
 
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Pelican Technical Article:

Brake Master Cylinder Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$250

Talent:

***

Tools:

1mm line wrench, 13mm universal socket, T20 Torx bit socket

Applicable Models:

R52 MINI Cooper Convertible (2007-08)
R52 MINI Cooper S Convertible (2007-08)
R56 MINI Cooper Hatchback (2007-11)
R56 MINI Cooper S Hatchback (2007-11)
R57 MINI Cooper Convertible (2009-11)
R57 MINI Cooper S Convertible (2009-11)

Parts Required:

Brake fluid, brake cleaner, brake master cylinder

Hot Tip:

Bleed vehicle twice to ensure all air is removed from system

Performance Gain:

Good brake operation

Complementary Modification:

Replace worn brake parts

MINI R56 service brakes consist of hydraulic brake calipers and rotors, one at each wheel. When the brake pedal is pressed, brake fluid is forced out of the brake master cylinder and through the brake lines to each brake caliper. Pistons in the calipers push out and clamp brake pads against the brake rotors (or discs), thus slowing down the vehicle. A vacuum assisted brake booster multiplies the braking force exerted by the driver at the brake pedal.

If the brake master cylinder cannot create enough pressure to clamp the brake pads firmly against the brake rotors, the brakes will have a poor feel. Over time seals get worn in the master cylinder and can leak. In this tech article we will show you how to replace the brake master cylinder in a few easy steps.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

MINI R56 service brakes consist of hydraulic brake calipers and rotors, one at each wheel.
Figure 1

MINI R56 service brakes consist of hydraulic brake calipers and rotors, one at each wheel. When the brake pedal is pressed, brake fluid is forced out of the brake master cylinder (red arrow) and through the brake lines to each brake caliper. Pistons in the calipers push out and clamp brake pads against the brake rotors (or discs), thus slowing down the vehicle. A vacuum assisted brake booster multiplies the braking force exerted by the driver at the brake pedal. The master cylinder (red arrow) is located beneath the wiper cowl.

Remove the wiper blades and left side wiper cowl (red arrow).
Figure 2

Remove the wiper blades and left side wiper cowl (red arrow). See out tech article on wiper assembly replacing.

Remove the brake fluid reservoir cap.
Figure 3

Remove the brake fluid reservoir cap. Lever out the reservoir screen using a small flathead screwdriver (red arrow). Using a fluid extractor, remove all of the fluid from the reservoir (green arrow).

Working at the brake master reservoir, disconnect the electrical connector (red arrow) by squeezing the release tab and pulling it straight off.
Figure 4

Working at the brake master reservoir, disconnect the electrical connector (red arrow) by squeezing the release tab and pulling it straight off. Then detach the clutch master cylinder line (green arrow) (if equipped) by levering it off (inset) with the rubber seal.

Allow the remaining fluid in the reservoir to drain into a container (red arrow).
Figure 5

Allow the remaining fluid in the reservoir to drain into a container (red arrow).

Using an E7 Torx bit socket (red arrow), remove the brake fluid reservoir-mounting bolt (green arrow).
Figure 6

Using an E7 Torx bit socket (red arrow), remove the brake fluid reservoir-mounting bolt (green arrow).

Now you can lift the reservoir up (red arrow) to detach it from the master cylinder.
Figure 7

Now you can lift the reservoir up (red arrow) to detach it from the master cylinder. You may need to move it side to side to free the seals.

Next, the steel lines have to be detached from the master cylinder.
Figure 8

Next, the steel lines have to be detached from the master cylinder. Use a 11mm line wrench to loosen the lines (red arrows); then unscrew and remove them.

Using a 13mm universal socket on a long extension, remove both master cylinder nuts (red arrows).
Figure 9

Using a 13mm universal socket on a long extension, remove both master cylinder nuts (red arrows).

Once you remove the nuts, lift the master cylinder off the brake booster while pulling the lines out, if still inserted.
Figure 10

Once you remove the nuts, lift the master cylinder off the brake booster while pulling the lines out, if still inserted. You will have to pull it away from the booster (red arrow) to break the vacuum seal of the booster. Pull the master cylinder straight out. Install the new master cylinder to the brake booster and install the mounting nuts finger tight. Install the brake lines by hand. Be sure not to cross-thread them. The lines should easily thread into the master. Once the lines are finger tight, tighten the master cylinder mounting nuts and then the lines. Bleed the brake system and test your brakes before taking the vehicle out for a drive. See our tech article on brake bleeding to help with that portion of the procedure.


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