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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:

$150

Talent:

***

Tools:

11mm, 12mm line wrenches, 15mm wrench, 13mm universal socket, T25 Torx bit socket

Applicable Models:

BMW 525i/xi Sedan (2004-07)
BMW 528i xDrive Sedan (2009-10)
BMW 528i/xi Sedan (2008-10)
BMW 530i/xi Sedan (2004-07)
BMW 530xi Wagon (2006-07)
BMW 535i xDrive Sedan/Wagon (2009-10)
BMW 535i/xi Sedan (2008-10)
BMW 535xi Wagon (2008)
BMW 545i Sedan (2004-05)
BMW 550i Sedan (2006-10)
BMW M5 Sedan (2006-10)

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 E60 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 brake 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.

Remove the cabin microfilter and microfilter housing (red arrow).
Figure 1

Remove the cabin microfilter and microfilter housing (red arrow). See our tech article on engine covers removing.

Remove the brake fluid level sensor electrical connector by releasing the locking tab and pulling it off.
Figure 2

Remove the brake fluid level sensor electrical connector by releasing the locking tab and pulling it off.

Remove the brake fluid reservoir cap.
Figure 3

Remove the brake fluid reservoir cap.

Using a fluid extractor, remove all of the fluid from the reservoir.
Figure 4

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

Vehicle with manual transmission: Working at the left lower side of the reservoir, pull off the hose (red arrow).
Figure 5

Vehicle with manual transmission: Working at the left lower side of the reservoir, pull off the hose (red arrow). This hose feeds hydraulic fluid to the clutch master cylinder. Once detached, plug the hose to prevent debris from entering the hose.

Next, the steel lines have to be detached from the master cylinder.
Figure 6

Next, the steel lines have to be detached from the master cylinder. The lines go up and over the master cylinder. Luckily, there is a junction you can remove them from. Starting at the rear line, counterhold the 15mm union while loosening the 12mm line nut (blue arrow). Then repeat the step for the front line (red arrow), by counter holding the 15mm union while loosening the 11mm line nut.

Once loose, slide the nuts away from the unions (green arrow).
Figure 7

Once loose, slide the nuts away from the unions (green arrow).

Below the fluid reservoir are the right (red arrow) and left (blue arrow) 13mm master cylinder mounting nuts.
Figure 8

Below the fluid reservoir are the right (red arrow) and left (blue arrow) 13mm master cylinder mounting nuts. Using a 13mm universal socket on a long extension, remove both nuts.

Once you remove the nuts, lift the master cylinder off the brake booster while pulling the lines out of the unions.
Figure 9

Once you remove the nuts, lift the master cylinder off the brake booster while pulling the lines out of the unions. You will have to pull it away from the booster to break the vacuum seal of the booster. Pull the master cylinder straight out. Then tilt the reservoir toward the right to fit it out of the body.

The next step only has to be performed if your new master cylinder did not come with a reservoir.
Figure 10

The next step only has to be performed if your new master cylinder did not come with a reservoir. Using a T25 Torx bit socket, remove the brake fluid reservoir-mounting bolt (blue arrow). Now you can lift the reservoir up to detach it from the master cylinder. Once detached, install in the reverse order of removing to the new master cylinder. Continue for all master cylinders: remove both steel lines (red arrows) and transfer them to the new master cylinder. Leave them snug but not tight, to allow for adjustment when connection to the unions. 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 union. 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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Comments and Suggestions:
carrot Comments: Is this process the same for the e90/e91?
July 30, 2015
  Followup from the Pelican Staff: No, it is different. I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799.- Nick at Pelican Parts
 

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Page last updated: Wed 12/7/2016 02:42:35 AM