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Master Cylinder Replacement
 
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Pelican Technical Article:

Master Cylinder Replacement

Time:

3 hr

Tab:

$100 to $300

Talent:

***

Tools:

Brake bleeder, torque wrench

Applicable Models:

 
Porsche 986 Boxster (1997-04)
Porsche 986 Boxster S (2000-04)
Porsche 987 Boxster (2005-12)
Porsche 987 Boxster S (2005-12)
Porsche 987 Cayman (2007-12)
Porsche 987 Cayman S (2006-12)

Parts Required:

Master cylinder, brake fluid

Hot Tip:

Make sure that you keep all brake fluid away from your paint

Performance Gain:

Better braking, no more leaky master cylinders

Complementary Modification:

Replace brake booster, install stainless steel brake lines
101 Performance Projects for Your Porsche Boxster

This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your Porsche Boxster. The book contains 312 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 950+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Boxster owner's collection. The book is currently available and in stock now. See The Official Book Website for more details.

Without a doubt, your brakes are one of the most important systems on the car. The heart of the brake system is the master cylinder, which controls the hydraulic pressure of the entire system. Unfortunately, over many years, the master cylinder has a tendency to wear out and leak. The leakage can occur internally or externally, resulting in a weakened braking system. If you have any problems with your brakes, and you think that it's related to the master cylinder, you should probably replace it.

The master cylinder is located in the front trunk area, on the driver's side, under a large plastic panel. To gain access to the master cylinder, you need to remove this panel. Begin by pulling up the hood seal and removing the three Phillips head screws located on the top of the panel. Rotate the slotted plug on the lower front corner of the panel and remove it, disconnecting the trunk lamp harness as you go. Now, remove the strainer from the brake fluid reservoir and then remove brake fluid using a turkey baster or a suction device. Or, you can also bleed the entire system of fluid by emptying the brake fluid out of one of the caliper bleed screws (see Pelican Technical Article: Bleeding Brakes). Be aware that some residual fluid will remain inside of the master cylinder, and that brake fluid is very damaging to paint. Disconnect the brake fluid level sensor from the reservoir.

Now you need to remove the reservoir. Disconnect the clutch master cylinder supply line: you will need to push in the press-fit connector with a small wrench carefully as you pull on the line. If you are not replacing the reservoir, then I recommend just leaving it connected and pushing the reservoir off to the side. Simply pull up on the reservoir to remove it from the o-rings that seal it to the master cylinder.

With the reservoir disconnected, place a towel under the master cylinder and disconnect the two brake line fittings. As with the installation of new flexible brake lines, it is very important not to strip out the fittings on the lines. You should always use an flare-nut wrench to remove the fittings from the master cylinder. See Project 54 for more details. It's also a wise idea to spray the area with some WD-40 or other lubricant if the lines seem to be heavily corroded. Cap the open brake lines with plastic covers to prevent brake fluid leakage. Remove the two nuts that attach the master cylinder to the brake booster, and you should be able to remove the master cylinder.

Installation is basically the reverse of removal. If you are replacing your ABS control unit or your brake booster, then at this point, see Project 57 for instructions on how to accomplish that task.

When the master cylinder is reinstalled, it's time to bleed your brake system. You may want to dry bleed the master cylinder on the bench in order to prime it before you start the install. For more information on bleeding your brakes, see Pelican Technical Article: Bleeding Brakes. Following the bleeding of the brakes, reassemble all the surrounding parts in the trunk that you have disassembled, and make sure that everything is tightened. Reinstall all the carpets and fasteners.

When you are ready to drive the car, make sure that you test the brakes beforehand. Don't drive near other cars, and prepare to use the emergency brake if necessary. It's probably a wise idea to bleed the brakes again a few days after you install the new master cylinder to make sure that you have gotten all of the air out of the brake system.

The master cylinder is hidden behind a plastic panel located in the front trunk.
Figure 1

The master cylinder is hidden behind a plastic panel located in the front trunk. Remove the plastic screws that hold the trunk liner down (blue arrow), and pull the liner out. There is a front trunk lamp (red arrow) embedded in the liner: remember to unplug the harness connected to this lamp.

Here's what you will see when you remove the front trunk liner.
Figure 2

Here's what you will see when you remove the front trunk liner. The purple arrow shows the vacuum-powered brake booster, which is the muscle behind the power-brake system. The orange arrow shows the brake fluid reservoir, which supplies hydraulic fluid to both the brake and clutch systems. The red arrow shows the ABS hydraulic control unit. The white arrow points to the master cylinder. The yellow arrow indicates the connection for the reservoir level sensor, and the green arrow shows the vacuum line that powers the brake booster. Finally, the light blue arrow shows the electrical connector that plugs into the front trunk lamp.

Shown here is a close-up of the master cylinder connections.
Figure 3

Shown here is a close-up of the master cylinder connections. First, empty out the reservoir, and then disconnect the clutch system supply tube (green arrow). Then, disconnect the two brake lines attached to the side of the master cylinder. Only use a flare-nut wrench (blue arrow, inset) as you otherwise may end up damaging the connectors on the lines.

With the brake lines disconnected, and the reservoir removed from the top of the master cylinder, remove the two nuts that fasten the master cylinder to the brake booster (yellow arrows).
Figure 4

With the brake lines disconnected, and the reservoir removed from the top of the master cylinder, remove the two nuts that fasten the master cylinder to the brake booster (yellow arrows).

Shown here is a brand new master cylinder with five protective caps attached.
Figure 5

Shown here is a brand new master cylinder with five protective caps attached. Carefully remove the caps right before you are ready to install the unit and/or the brake lines.

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Comments and Suggestions:
Medtech Comments: Summary of tools needed 987 Spyder:
1. 13mm open end wrench - for brake lines
2. 22mm socket - for nut that attaches master cylinder
3. T-45 torx - only if you need to remove the brake booster for some reason
September 18, 2016
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
Medtech Comments: What size and type wrench do I need to disconnect the MC from the brake booster?
September 16, 2016
  Followup from the Pelican Staff: Summary of tools needed 987 Spyder:
1. 13mm open end wrench - for brake lines
2. 22mm socket - for nut that attaches master cylinder
3. T-45 torx - only if you need to remove the brake booster for - Nick at Pelican Parts
 
bar10dah Comments: Wayne, please delete my question above. Reread your text in the paragraphs above and saw it's a push connector. Not sure how I missed that the first time I read it.
June 14, 2012
  Followup from the Pelican Staff: No problem, we'll leave it up, it may help someone. Thanks for the follow up. We appreciate it. - Nick at Pelican Parts  
bar10dah Comments: In figure 3, how do you disconnect the clutch line, represented by the green arrow. Does it simply pull out?
June 14, 2012
  Followup from the Pelican Staff: Press the gray ring in and hold wehile pulling the line out. - Nick at Pelican Parts


 

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