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Clutch Hydraulics Overhaul (Master Cylinder & Slave Cylinder Replacement)
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Pelican Technical Article:

Clutch Hydraulics Overhaul (Master Cylinder & Slave Cylinder Replacement)


2 hours2 hrs






Socket set

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:

Clutch slave cylinder

Hot Tip:

Replace when performing a clutch job

Performance Gain:

Reliable shifting and clutch operation

Complementary Modification:

Bleed brake system
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.

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 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.

In the front trunk, under the plastic cover you will find the clutch master cylinder.
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.
Figure 2

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.
Figure 3

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.
Figure 4

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.

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Comments and Suggestions:
Grant Comments: Im having issues with my 2010 Cayman S. Intermittently clutch slips and occasionally becomes hard to shift. Mostly happens at autocross events. Im wondering if exhaust heat is overheating fluid in line going to clutch slave. The pedal itself at times doesn't return fully . Doesnt happen often but when it does clutch doesnt engage fully and shifting can be difficult as well. Im upgrading fluid and shielding clutch lines to see if that addresses the issues. If not whats best guess to whats failing? Master cylinder or clutch slave. Car only has 40,000 miles and issue has been going on since about 36,000.
August 9, 2016
  Followup from the Pelican Staff: Slipping would not be overheated fluid, that would be a worn out clutch. - Nick at Pelican Parts  
Alex Comments: 2006 Cayman S
Is there a way to adjust the point of engagement? I was going to attempt this but my problem is opposite of what most are having. My clutch engages about 1-2 inches from fully released. It used to engage closer half the pedal travel. Would swapping out the master and/or slave alleviate this issue?

Other than clutch chatter from the lighten flywheel, there are no other issues... no slipping no grinding.
June 30, 2016
  Followup from the Pelican Staff: No adjustments. The clutch is likely work out. - Nick at Pelican Parts  
997porker Comments: Hi
Have a 997 turbo. Have changed slave, accumulator, master and new clutch. Power springs
Pedal is all fine when engine if off, run engine all fine. Start to move and use the clutch. The pedal has a popping, notchy sensation at the top end return. Around the last 5-8mm. Has been bled many times.....thinking it may be a faulty slave?
May 14, 2016
  Followup from the Pelican Staff: Slave or pressure plate issue. See if you can apply some pressure to the clutch fork in either direction to change the notchy feel, when pressing the pedal. - Nick at Pelican Parts  
livvy1960 Comments: Another Clutch Pedal Problem !
I have replaced my transmission, Dual Mass Flywheel, Clutch Plate and Pressure Plate and have nothing at the Clutch Pedal.
On re-assembly I pushed the Slave Master Cylinder into the housing without first undoing the nipple to release any pressure and this was when I noticed the problem.
I bled the system and still no luck.
I have double checked slave cylinder engagement and all looks ok and I can see the release arm.
I have replaced the master cylinder never again! and re bled the system with the pedal to the floor and still no luck.
I am now thinking to change the slave cylinder approx £35 new as a matter of general preventative maintenance and hope this solves the problem.
In the meantime can you provide an step by step instruction guide on how to bleed the clutch system and do you have any tips / suggestions on how to overcome this issue.

To gain access the rear wheels are on ramps
The system has been emptied and refilled at least twice

Many Thanks
June 15, 2015
  Followup from the Pelican Staff: Ok when I replace a slave cylinder I usually connect the slave cylinder hose, and then let the slave cylinder hang down from the hose with the bleeder open. Keep the brake fluid reservoir topped up and watch the bleeder nipple bubble. When the bubbling stops, close (tighten) the bleeder screw, and install the slave cylinder. NOW, go pump the pedal three times (you should have at least a partial pedal it may not be perfect yet) then on the 3rd pump hold the pedal down and have an assistant open the bleeder screw, until fluid squirts out, then close the bleeder. Pull the clutch pedal up from the floor and then pump three times and repeat this process until the pedal feels good. - Casey at Pelican Parts  
Andy Comments: The clutch pedal seems to stick just after the biting point the clutch engages and works just fine there is no slipping or noise. It has a distint change in pressure as you lift it up, the last part seems to stick then Pop up as the car warms or on a longer trips it seems to get better?

April 21, 2015
  Followup from the Pelican Staff: Sounds like the master cylinder is starting to go. If it lacks the strength to return the pedal, you will have just what you described. - Nick at Pelican Parts  
Al Comments: I'm sorry: It is a Boxster 2002, 2.7lt all clutch parts new disc, plate, fork, dual mass flywheel, slave cylinder
February 21, 2015
  Followup from the Pelican Staff: There may be air trapped in the hydraulic system. Try bleeding it. - Nick at Pelican Parts  
Al Comments: In the morning, when car and engine cold, The clutch is working fine but still have to press pedal all the way down in order to shift, when warm it become more difficult to shift and have to push pedal all the way down. What seems to be the problem?
February 20, 2015
  Followup from the Pelican Staff: You didn't mention what vehicle you have. COuld be a worn clutch. - Nick at Pelican Parts  
Red Comments: During a clutch disk/pressure plate/flywheel replacement, I disconnected the fluid line where it plugs into the slave cylinder, draining at least a cup or two of fluid. I just bled the clutch hydraulics after reinstalling the transmission. I depressed the clutch pedal, as instructed in this guide and the Bentley manual, and it stuck to the floor as expected.

After bleeding the clutch for several minutes, until no more bubbles appear, the clutch pedal is still stuck to the floor. I tried pulling it up, and it snapped back up. I then tried pushing it down, and it snapped back down. This is all before starting the engine.

Is this expected? I would think after flushing the clutch the pedal would operate as usual, even before starting the car.
February 16, 2015
  Followup from the Pelican Staff: Pull the pedal up, then try pumping fluid through the system using a pressure bleeder. Clutch masters are tough to bleed. Sometimes I will hold the slave in place during the initial bleeding steps to get the first but of air out. Then help the slave to fully extend during the next steps. This seems to get the air out. - Nick at Pelican Parts  
Al Comments: boxster 2002- 2.7 lt
December 24, 2014
  Followup from the Pelican Staff: No software needed to bleed the clutch. - Nick at Pelican Parts  
Al Comments: one more question: any electronic or software setting OBD2 connection required on the cluth bleeding process?
Or just the power bleeder process
December 21, 2014
  Followup from the Pelican Staff: Not likely. What vehicle are you working on? - Nick at Pelican Parts  
Al Comments: I also changed the slave cylinder, because on first attempt started bleedimg from the retainer, gasket or O ring that holds the center shaft that push the fork inside the transmission shell.
by the way ...great site, valuable information
December 20, 2014
  Followup from the Pelican Staff: Gotcha, see my follow up below. - Nick at Pelican Parts  
Al Comments: Hello, I got the clutch parts from "pelican parts" I changed the parts buy still have problems with the bleeding,
I connected the power bleeder charged around 20 psi with pressure on the pedal then go back to bleeder valve and let all bubbles out, less than a minute then closed the valve and disconnect power what moment should I depress the pedal?
Still half way and not working
December 20, 2014
  Followup from the Pelican Staff: How I do it:
Use a vacuum pump or pressure bleeder to fill the system and remove most of the air. Then help the slave extend the clutch fork to extend the slave rod to it's full extent, then press the pedal and hold, open bleeder, close bleeder, repeat until bled. Do not press the pedal more than one time per bleeder opening. - Nick at Pelican Parts
Al Comments: helllo: what is the procedure to blled the clutch? on a boxster 2002 2.7 litre.
I changed the clutch, but have problems with the pedal
December 12, 2014
  Followup from the Pelican Staff: The article you commented on suggests seeing this article for bleeding: - Nick at Pelican Parts
Waynecharper Comments: So my 98 Porsche boxster and I were driving down the highway when I went to shift the clutch pedal was stuck to the floor. After getting under the car I saw that the slave cylinder was bad and replaced it. Now we are bleeding the system and when we close the valve on the slave cylinder we can't press down the pedal all the way. when we open the cable we can press the clutch pedal all the way down but it slowly ducks it's self to the floor of the car and has to be pulled up. Is there still air in the lines? We aren't using a caving bleeder just Manuel bleeding. Should we get a vaccum bleeder?
November 3, 2014
  Followup from the Pelican Staff: So the pedal is suck up when the bleeder isn't open? There may be an issue with the pressure plate. Check if the clutch fork is jammed. - Nick at Pelican Parts  
- Read other comments, many provide tips.
- Screen on MC will prevent turkey baster from effectively removing fluid. Therefore, when disconnecting top line on frunk side of MC, have plug ready to block fluid flow. mine was rubber cone shaped A spill is not preventable, but plugging line will help contain it. Roll of paper towels for spill.
- The lower line on MC is held by clip from the side. Long needle nose plyers can help get the clip started into the slot on reinstallation, then press clip to seat.
- 10MM Racheting wrench mentioned by others works great to remove bolts
- Removing clip on clevis pin is the hardest part of the job because your vision is VERY limited. I used mirrors to get a better look at where I needed to pry to remove clip.
- Don't worry about disconnecting line from inside the interior while MC is in place. Once unbolted and pin is removed, just pull the MC out top line will pop through rubber grommet at firewall keep MC tipped so that the lines point up to prevent spilling.
- Then, once out, top line on MC is EASY to unclip
October 29, 2014
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
V8Boxster Comments: Your site is great and has lots of good information and photos. I couldn't have done the work without it.

However, has anyone else found working on the clutch master cylinder a major pain!? Unless you've got the dash apart already it's almost impossible to get everything back together. You simply can't see half of what you're trying to do because everything is so close under the dash. Twice now I've leaked lots of brake fluid all over my carpets because the top line to the cylinder wasn't connected, though I think it is. And, how the h3ll do you get that tiny clip in!? I've had to resort to folding a piece of duct tape to the tip of my finger, then attaching the clip to the piece of tape, then pushing the clip into the slot-even though I can't even see where the h3ll the d@mn slot is.
October 14, 2014
  Followup from the Pelican Staff: It is always hard working in confined spaces. usually worse the first time you perform a repair, then easier each time after. experience is key here. Glad you got it done, even though it was a pain.

- Nick at Pelican Parts
mahoskic Comments: Does anyone have a photo of what the clutch line end that goes into the slave cylinder looks like?
i had to replace my slave cylinder and now the line will not stay in the slave cylinder.
i am guessing that i may have lost a piece or i just keep getting the wrong part.
September 28, 2014
  Followup from the Pelican Staff: I don't.

I opened a post in our forums. A Pelican community member may be able to answer your question.
- Nick at Pelican Parts
D.B. Comments: Like many others, I had difficulty installing the slave cylinder this was after RMS, IMSB, and clutch replacement. I just couldn't get the slave cylinder to go far enough in. But after a light application of some grease around the outside of the slave cylinder rubber boot where it meets the hole in the transmission, it went right in with ease.
June 23, 2014
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
Shawn Comments: Hi there, where can I find the tiny flared plastic piece that is supposed to be on end off fluid line going into slave cylinder? Line won't lock without it, and it may have been tossed still inside old cylinder?
June 4, 2014
  Followup from the Pelican Staff: If it is lost, you may have to buy a new line or slave cylinder.
Give our parts specialists a call at 1-888-280-7799. They can help you find the right part. - Nick at Pelican Parts
Shawn Comments: Thanks for the site, greatinfo. Replaced clutch slave cylinder in a new to us 2002 Boxster. Used the Motive power bleeder. All seemed well until I pushed in on the clutch pedal, felt a pop, and fluid started hitting the floor. Pulled slave back out today, and the 4 plastic tabs that look like they hold the guts in had all broken off. Did I do something wrong? Is there a problem inside the clutch housing? Followed instructions, and part bolted in properly. Now have to get another slave and would hate for same thing to happen. Thanks, Shawn
May 30, 2014
  Followup from the Pelican Staff: It's possible it wasn't properly engaged with the clutch fork. Why did you replace it, due to a leak? If so, I would think the mechanical clutch components are Ok and the slave was installed wrong. - Nick at Pelican Parts  
Shady_Grove Comments: referring to Figure one in this article, is there a special tool to remove the master cylinder fill line from the master cylinder? It doesn't have a regular clip.
April 11, 2014
  Followup from the Pelican Staff: Use a small pick and pull the retaining clip out of the line. - Nick at Pelican Parts  
mgfranz Comments: Is there a way to verify if you have a failing/failed slave cylinder before ordering a new one? My vehicle was shifting fine then all of a sudden it wouldn't go into any gear, nor would it allow me to shift out of a gear once I power shifted into a gear.

This is of course without the obvious leaks...
April 6, 2014
  Followup from the Pelican Staff: You can remove the line from the master, then block it off with a plug. Once blocked, press the clutch pedal. If it is hard, the master is OK and the slave is likely at fault. If the pedal is soft, the master is faulty. Keep in mind, a lot of times they fail together or shortly after one another. - Nick at Pelican Parts  
Les. D Comments: Hi. I am in the process of ordering a replacement clutch slave cylinder for a 1998 2.5 Boxster. The information states I also require a new feed pipe and bracket as Porsche changed the design. This adds around £100 to the price of parts. Is this correct, as it's not mentioned in the article.
Great site by the way. Excellent information!
January 30, 2014
  Followup from the Pelican Staff: Yes, follow the directions in the article as far as what part you need. I am not sure of the cost increase, Give our parts specialists a call at 1-888-280-7799. They can help you find the right part and determine the additional cost. - Nick at Pelican Parts  
Struggling Comments: I'm a big fan of your site and all of the parts and helpful information has allowed me to work through many projects on my 2001 Boxster S. A burst flex line led me to replace the flex line, MC and Slave thinking the MC and Slave is soon to follow. I'm having trouble getting the slave in. I can compress the slave easily enough but it is still about 3/8" from aligning with the bolt hole. No amount of effort seems to be enough to push the slave straight into the hole for the bolt hole to reach alignment. I've removed a section of the exhaust for better access and had several stronger chaps give it a try but to no avail. This does not seem right. Could there be a problem the clutch/pressure plate? Any advice?
January 19, 2014
  Followup from the Pelican Staff: I know this can be tough as I have been there. You just have to push HARDER to compress it. - Nick at Pelican Parts  
Frustrated Comments: It would be nice to know where the slave cylinder is. "located on the left side of the transmission" is pretty nebulous. I picture from a person's perspective under a jackup car would be nice rather than a motor thats been removed from the car in a garage.
December 30, 2013
  Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help.
- Nick at Pelican Parts
pavel Comments: I've got fluid coming out from bottom hole in clutch assembly - mostlikely salve cylinder need to be replaced. I can barely see it on transmition. Also removed left rear wheel to get easier access but it did not help. How to get better access to replace cylinder?
November 6, 2013
  Followup from the Pelican Staff: To improve access, you can remove the transmission mount. Place a jack under the transmission, then remove the mount fasteners. Then lower the transmission an inch or two. Don't go too far and monitor the vehicle to be sure no hoses or wires are stretched.- Nick at Pelican Parts  
JC in Chicago Comments: Thanks for this great site and your book on the Boxster. I'm replacing the transmission on my '02 S and I cannot get the clutch slave cylinder to go into place. The clutch worked fine when the trans was removed but will not return to its spot, it will not go far enough into the hole for the retaining bolt to match up with the bolt hole. Is there an angle to use or a specific instruction for replacing the slave cylinder? Thank you in advance for your help, and of course for your site and store, great assets all.
August 27, 2013
  Followup from the Pelican Staff: When installing, press it stright it. Assuming you did not open the line, there will be pressure in te hydraulic system fighting you. You'll want to slowly compress the salve piston by pressing in into the clutch, once it compresses, installing the bolts. Be sure the bolts are aligned properly, thread them in by hand until flush. - Nick at Pelican Parts  
louie the 13th Comments: How do you bleed the slave cylinder?
Please explain in detail.
I just ordered the book also thanks.
May 11, 2013
  Followup from the Pelican Staff: The slave cylinder repair info is here:

The tech article states to use the bleeding procedure located here: - Nick at Pelican Parts
Stroked & Blown Comments: * T-25 torx bit to remove trim above hydraulic lines

* I removed the trim around the hydraulic fluid reservoir to better see when I'd removed enough fluid. This isn't required, but helpful.
* There was a filter trim piece in the reservoir filler. I gently pried this out with a small screw driver. It takes a lot of finesse.
* The master cylinder clips pop on-off sideways. Inspect your new MC to understand the orientation prior to crawling into the footwell. Both my old and new ones are blue. Use the picks to pry off the clips.
* Use paper towels on both the front side of the firewall, under the connections identified in Fig. 1 and in the footwell. Keep them their until after the old MC is removed.
* There is a top clip on the MC between the two bolts that isn't mentioned in the article. This is tough to see. Un-clip it BEFORE un-bolting the MC. This will leak fluid after being un-clipped.
* Use the 10mm ratcheting wrench identified below to un-bolt the MC.
* The clevis pin must sit into a recess matching the bolt head shape. A 9mm wrench helps align the pin.
* Use gloves and change them when they get fluid on them. They're $.20 a pair and a respray is thousands.
August 16, 2012
  Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it. - Nick at Pelican Parts  
Stroked & Blown Comments: Ordered the book and parts and went at changing my clutch master cylinder last night. The book was very helpful in outlining what needed to be done.
A few comments for others attempting this job:
* 10mm ratcheting wrench to un-bolt the master cylinder:
Un-bolting the MC with a traditional wrench would take MUCH longer given the space constraints. A 1/4" drive ratchet on w/ 10mm socket or swivel socket on an air wrench may also work.
* Pick set for removing clips:
* Low profile shop light to see under the dash
* 9mm wrench to help re-align the clevis pin on installation
* 11mm flare wrench to open SC bleeder screw
* Box of rubber gloves
* Turkey baster
* Phillips head screw driver optional - if taking off reservoir trim
August 16, 2012
  Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it. - Nick at Pelican Parts  
william Comments: I find everything very well put together ,thank you
August 18, 2010
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help. - Nick at Pelican Parts  

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