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Brake Master Cylinder Replacing
 
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Pelican Technical Article:

Brake Master Cylinder Replacing

Nick Czerula

Time:

2 hours2 hrs

Tab:

$250

Talent:

***

Tools:

11mm line wrench, 13mm socket, T25 Torx bit socket

Applicable Models:

BMW Z4 Convertible (2003-06)
BMW Z4 Coupe (2006)

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

BMW Z4 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 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. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

The master cylinder is located at the wiper cowl.
Figure 1

The master cylinder is located at the wiper cowl. Start by removing the coolant reservoir. Remove the brake fluid reservoir cap. Lever out the reservoir screen using small flathead screwdriver (inset).

Using a fluid extractor, remove all of the fluid from the reservoir.
Figure 2

Using a fluid extractor, remove all of the fluid from the reservoir. When refilling, be sure the reservoir is filled to the MAX level (red arrow).

Working at the brake master reservoir, disconnect the electrical connector (red arrow) by squeezing the release tab and pulling it straight off.
Figure 3

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 (red arrow) (if equipped) by pulling it straight off.
Figure 4

Then detach the clutch master cylinder line (red arrow) (if equipped) by pulling it straight off. Plug the line to prevent debris from entering (inset). Allow the remaining fluid in the reservoir to drain into a container.

Next, the steel lines have to be detached from the master cylinder.
Figure 5

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

Plug the brake lines once removed (red arrows).
Figure 6

Plug the brake lines once removed (red arrows).

Using a T25 Torx bit socket, remove the brake fluid reservoir mounting bolt (red arrow).
Figure 7

Using a T25 Torx bit socket, remove the brake fluid reservoir mounting bolt (red arrow).

Now you can lift the reservoir up to detach it from the master cylinder.
Figure 8

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

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

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

Once you remove the nuts, pull the master cylinder (red arrow) out of the brake booster.
Figure 10

Once you remove the nuts, pull the master cylinder (red arrow) out of the brake booster. You will have to pull it away from the booster 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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Page last updated: Fri 12/9/2016 03:03:42 AM