Pelican Technical Article: Clutch Hydraulics Overhaul (Master Cylinder & Slave Cylinder Replacement) Wayne R. Dempsey
Time: 2 hours
Tab: $150
Talent:
Tools:
Socket set
Applicable Models:
986 Boxster (1997-04) 987 Boxster (2005-08)
Parts Required:
Clutch slave cylinder
Hot Tip:
Replace when performing a clutch job
Performance Gain:
Reliable shifting and clutch operation
Complementary Modification:
Bleed brake system
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.
Check out some other sample projects from the book:
The Boxsters have a hydraulic clutch engagement system - there are no cables involved with the actuation of the clutch. Although this actually creates a more reliable clutch system over time, there can be a failure or break-down of the system if the slave or master cylinder get old and begin to leak or fail. A spongy feel to the clutch pedal, grinding of gears when shifting, long pedal travel, and hydraulic leaks under the car are all signs that one or more components of the system have failed. The first place I like to start is the clutch slave cylinder, as it is easy and inexpensive to replace.
Replacement of the slave cylinder is also pretty easy. Its location is easy to get to from underneath the car. Start by jacking up the car (Pelican Technical Article: Jacking Up and Lifting the Boxster on Jack Stands). The slave cylinder is located on the left side of the transmission: a single nut fastens it to the transmission. Begin by disconnecting the hydraulic line from the cylinder. Make sure you use a flare-nut wrench to remove the hose. These hydraulic fittings have a tendency to strip if you use a regular wrench. Also, inspect the clutch slave line - you might want to replace it if it's bulging, or shows signs of cracking in the rubber. Before you disconnect the line, make sure that you have a drip pan to catch the fluid that will leak out.
Now, remove the 13mm head bolt that holds the cylinder to the transmission. The slave cylinder should remove easily. Install the new one and reattach the clutch fluid line. Place a little bit of white lithium grease on the tip of the slave cylinder prior to installation.
Replacement of the clutch master cylinder is fairly straightforward. Begin by removing the plastic cover to the left of the battery in the front trunk. Using a turkey baster, remove enough brake fluid to lower the level in the reservoir below the fill hole for the clutch master cylinder. Then disconnect both the supply line and the slave cylinder line (see Figure 1). Next, from underneath the dash disconnect the master cylinder from the pedal and unbolt it from the car (Figure 2). Have a whole bunch of paper towels handy to wipe up any spilled brake fluid: the stuff is very hazardous to your car's paint.
The system now needs to be bled. I like to use the Motive Products Power Bleeder (available from PelicanParts.com) for this task. For more information on using the Power Bleeder, see Project 48 on Bleeding Brakes. Fill up the brake fluid reservoir to the MAX level, and attach the power bleeder to the top of the master cylinder reservoir. Press in the clutch pedal. Pump up the pressure in the bleeder to about 22 psi. Move to underneath the car and attach your bleeder hose to the bleed nipple on the slave cylinder. Open the bleeder valve by turning it counter-clockwise and let the system bleed out until no more bubbles appear.
When finished, remove the bleeder system, lower the car, and try the clutch again. The pedal should have a good feel to it, and the clutch should engage normally. If you are still having problems, you should try replacing your clutch master cylinder next.
Figure 1
In the front trunk, under the plastic cover you will find the clutch master cylinder. Empty the fluid reservoir below the clutch fill hole, and then disconnect both the filler hose (red arrow) and the hydraulic line that leads to the slave cylinder (pry out the locking clip: yellow arrow).
From underneath the dash, remove the clevis pin (yellow arrow) and circlip that attaches the clutch master cylinder to the clutch pedal. Unbolt the two attachment bolts (green arrows) and slide the master cylinder out. The inset photo shows a brand new clutch master cylinder.
Shown here are the various components associated with the slave cylinder. The yellow arrow points to the slave cylinder and the green arrow is pointing to the bolt that attaches the slave cylinder to the transmission. The blue arrow shows the transmission backup lamp switch.
Here's a shot of the slave cylinder installed in the car. To disconnect the fluid line, simply remove the metal clip (yellow arrow), and pull the red line out of the bore. The green arrow points to the bleed nipple, which is required for bleeding air out of the clutch system.
