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Pelican Technical Article:
Bleeding Brakes
 

 
Time: 2 hours
Tab: $20
Talent: 
Tools:
Power Bleeder, 11mm wrench, floor jack & jack stands
Applicable Models:
986 Boxster (1997-04)
987 Boxster (2005-08)
Parts Required:
3+ quarts of brake fluid
Hot Tip:
Use different colored brake fluid so you know when your system is flushed
Performance Gain:
Quicker, firmer stopping
Complementary Modification:
Rebuild brake calipers
 
  

 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: 

Need to buy parts for this project? Click here to order!
  
     Bleeding brakes is not one of my personal favorite jobs. There seems to be a bit of black magic involved with the bleeding process. Sometimes it will work perfectly, and then other times it seems like you end up with a lot of air in your system. The best strategy to follow when bleeding your brakes is to repeat the procedure several times in order to make sure that you have removed all the trapped air from the system.

     The basic Boxster brake system with anti-lock brakes (ABS 5.3 and 5.7 without PSM) can be bled using traditional methods. For cars with traction control or Porsche Stability Management (PSM), you need to use the Porsche System Tester 2 (PST2) in order to activate the valves in the hydraulic unit during the bleeding process. If your car has a “PSM off” switch on the dashboard, then you will need to go to a shop that has a PST2 so that the brake system can be bled properly.

     There are currently two popular methods of bleeding the brake system, pressure bleeding, and vacuum bleeding. Pressure bleeding uses a reservoir of brake fluid that has a positive air pressure force placed on the opposite side of the fluid, which forces it into the brake system. Vacuum bleeding is where you fill the reservoir, and then apply a vacuum at the bleeder nipple to pull fluid through the system.

     The method that I've come up with combines the first method described above and yet another third finishing method. Basically, I advocate bleeding the system with the pressure bleeder, and then use a family member to stomp on the pedal to free up any trapped air in the system. If the family member really owes you big time, you will be the one stomping on the pedal, and they can spill brake fluid all over themselves. 

     The first step in bleeding your brakes is to jack up the car and remove all four wheels (see Pelican Technical Article: Jacking Up and Lifting the Boxster on Jack Stands). The next step is to fill the system with brake fluid. I recommend using colored brake fluid like ATE SuperBlue in order to determine when fresh fluid has been flushed through the entire system. One of my favorite tools for pressure bleeding is the Motive Products Bleeder. The system has a hand pump that you can use to pressurize the brake fluid to just about any pressure. A small gauge on the front of the brake fluid reservoir indicates the pressure of the brake fluid inside. The very large reservoir can hold about two quarts of brake fluid: more than enough for most brake flushing and bleeding jobs. Retailing for about $50 online from PelicanParts.com, the bleeder kit is a very useful and cost-effective tool to have in your collection.

     The system bleeds by pressurizing a bottle filled with brake fluid from air from an internal hand pump. The procedure is to add fluid, attach the bleeder to the top of the reservoir cap, and pump up the bleeder bottle to about 25 psi using the hand pump. This will pressurize the system. Check to make sure that there are no leaks around the bleeder, or where it attaches to the top of the master cylinder reservoir.

     Now start bleeding the system. Start with the right rear caliper, the one that's located furthest away from the master cylinder. Bleed the right rear caliper by attaching a hose to the bleed nipple, placing it in a jar, and then opening the valve by turning the bleeder nipple counter-clockwise with an 11mm wrench. Let the fluid flow out until there are no more bubbles. If you don't have a pressure bleeder system, you need to find someone to press on the pedal repeatedly to force fluid through the system. Another solution is to get a check valve and place it on the nipple while you stomp on the pedal (see Figure 3). This will work for getting fluid into the system but you will still need a second person for the final step - to make sure you have bleed the system completely. The Boxster calipers have two bleed nipples: bleed the outer ones first.

     When no more air bubbles come out, then move to the next caliper. Bleed them in this order: right rear caliper, left rear caliper, right front caliper, left front caliper. Bleeding in this order will minimize the amount of air that gets into the system.

     Repeat the process until you can no longer see any air bubbles coming out of any of the calipers. Make sure that you don't run out of brake fluid in your reservoir, or you will have to start over again. It is wise to start out with about a 1/2 gallon of brake fluid in the pressure bleeder, and another 1/2 gallon on the shelf in reserve. Depending upon your car, and the mistakes you may make, I recommend having an ample supply. Also, only use new brake fluid from a sealed can. Brake fluid is hydroscopic, meaning that it attracts water and water vapor, which diminishes its performance. Brake fluid containers left exposed to air will have the fluid inside compromised after a short period of time.

     If you had to replace the master cylinder, or if the system needs a large amount of fluid, then supplement the bleeding process by opening up the right rear nipple, and then pressing down on the brake pedal 2-3 times. Slowly release the pedal. Repeat for the other three corners of the car.

     During the bleeding process, it's very easy to forget to check your master cylinder reservoir. As you are removing fluid from the calipers, it will be emptying the master cylinder reservoir. If the reservoir goes empty, then you will most certainly add some air bubbles in to the system, and you will have to start all over. Keep an eye on the fluid level and don't forget to refill it. Make sure that you always put the cap back on the reservoir. If the cap is off, then brake fluid may splash out and damage your paint when the brake pedal is released. If you are using a pressure bleeder system, make sure that you often check the level of brake fluid in the bleeder reservoir so that it doesn't accidentally run dry.

     If you are installing a new master cylinder, it's probably a wise idea to perform what is called a dry-bleed on the workbench. This is simply the process of getting the master cylinder full of brake fluid and ‘wet.' Simply add some brake fluid to both chambers of the master cylinder, and pump it a few times. This will save you a few moments when bleeding the brakes.

     Now, make sure that all the bleeder valves are closed tightly. Disconnect the pressure system from the reservoir. Now, get your family member to press down repeatedly on the brake pedal at least five times, and then hold it down. Then open the bleeder valve on the right rear caliper. The system should lose pressure, and the pedal should sink to the floor. When the fluid stops coming out of the bleeder valve, close the valve, and then tell your family member to let their foot off of the pedal. Do not let them take their foot off until you have completely closed the valve. Repeat this motion for each bleeder valve on each caliper at least three times. Repeat this entire procedure for all the valves in the same order as described previously.

     I recommend that you use this procedure as a final step, even if you are vacuum or pressure bleeding. The high force associated with the pressure from the brake pedal can help free air and debris in the lines. If the brake fluid doesn't exit the nipple quickly, then you might have a clog in your lines. Brake fluid that simply oozes out of the lines slowly is a clear indication that your rubber lines might be clogged and constricted. Don't ignore these warning signs: check out the brake lines while you are working in this area (see Pelican Technical Article: Brake Line Replacement).

     Now, let the car sit for about 10 minutes. Repeat the bleeding process at each corner. The pedal should now feel pretty stiff. If the pedal still feels spongy, make sure that you have the proper adjustment on your rear calipers or drum shoes. Also, you may need a new master cylinder, have a leaky caliper, or have old spongy flexible brake lines.

     For cars with the standard ABS 5.3, the bleeding method detailed here works very well. If you find that your ABS equipped car feels spongy on the brake pedal, take the car to a deserted parking lot and engage the ABS system by stopping short a few times. Then go back and rebleed the system: it should take care of the spongy pedal.

     Another important thing to remember is that brake fluid kills: paint jobs that is. Brake fluid spilled on paint will permanently mar the surface, so be very careful not to touch the car if you have it on your hands and clothing. This of course, is easier said then done - don't bleed the system in a tight garage. The probability of spilling on yourself and then leaning against your car is too great. Rubber gloves help to protect yourself from getting it on your hands and your paint. If you do get a spot on your paint, make sure that you blot it with a paper towel - don't wipe or smear it. It's also important not to try to clean it off with any chemical or other cleaning solutions.
There are few little tricks that you can use when changing your brake fluid.
Figure 1
There are few little tricks that you can use when changing your brake fluid. The company ATE makes a brake fluid called SuperBlue that comes in two different colors. It's a smart idea to fill your reservoir (green arrow) with a different colored fluid, and then bleed the brakes. When the new colored fluid exits out of the caliper, you will know that you have fresh fluid in your system. Make sure that you use DOT 4 brake fluid in your car. The use of silicone DOT 5 fluid is not recommended for street use, and never mix DOT 4 and DOT 5 fluid together or severe component corrosion can occur. Shown here is the Motive Products Power Bleeder. Available for about $50 from PelicanParts.com, it is a huge time-saver when it comes to bleeding your brakes.
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Open the bleed nipple by loosening it in the caliper by about a quarter of a turn.
Figure 2
Open the bleed nipple by loosening it in the caliper by about a quarter of a turn. If you can fit a flare-nut wrench over the bleed nipple, then I recommend using one, to help avoid rounding out the nipple. Let the brake fluid run out of the caliper until no more bubbles appear (inset). You should also routinely flush and replace your brake fluid every two years. Deposits and debris can build up in the lines over time and decrease the efficiency of your brakes. Regular bleeding of your system can also help you spot brake problems that you wouldn't necessarily notice simply by driving the car. Also, never reuse brake fluid - always use new fresh fluid. In addition, don't use brake fluid that has come from an empty can that has been sitting on the shelf or sitting in your Power Bleeder for a while. The brake fluid has a tendency to absorb moisture when sitting on the shelf. This moisture 'boils' out of the brake fluid when you start using the brakes and can result in a spongy pedal.
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There is a relatively new product out called Speed Bleeders.
Figure 3
There is a relatively new product out called Speed Bleeders. These small caps replace the standard bleeder valves located on your calipers. The Speed Bleeders have a built-in check valve that eliminates the need for a second person when pedal bleeding the brakes. Simply open the bleeder valve for a particular caliper and step on the brake pedal. The Speed Bleeder will allow brake fluid to cleanly bleed out of the system without sucking air back in. When used in conjunction with a pressure bleeder system, you can achieve a pretty firm pedal bleeding the brakes by yourself. I still recommend using the two-person pedal-stepping method as a final procedure, simply because the high pressure from this method can help to unclog trapped air bubbles.
Large Image | Extra-Large Image
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Bonus Photos
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Comments and Suggestions:
TimComments: You discuss that the Boxster calipers have two bleed nipples. Based on the guidance in the book, one should bleed the outer nipples first. Once the outer nipple is complete, do you then bleed the inner nipple on that same caliper before moving to the next one? Or do you bleed all 4 outer nipples first and then return to bleed all 4 inner nipples following the caliper order specified in the projects book? Thanks
April 19, 2014
 Followup from the Pelican Staff: Bleed one caliper, at each fitting, then move onto to the next wheel. - Nick at Pelican Parts  
QuadComments: I have a 99 Boxster, lately with even short lived drives the disc brakes seem to be applying themselves and dramatically bogging down the car. I know the disks are hot both from smell and appearance. I have pulled the both rear discs off tonight to verify free movement and nor visial problems. They seem to be adjusted adequately. I have even run the car statically with powertrain engauged to eliminate the eliminate the possibility the parking brakes were sticking. It was only after driving the car again dynamically to have the fault return with the brakes slowly closing down and bogging the car. Is this a sign of bad brake fluid with water entraining? My next step is to bleed the system fully with new fluid. This has been very frustrating to me. I have the 101 projects book and visit this site often.
July 14, 2013
 Followup from the Pelican Staff: Yes water in the brake fluid will boil and give a "spongy" pedal when the brakes are hot. This could also be an issue with the ABS and traction control systems thinking the wheels have lost traction and the traction control is trying to correct the possible spinning wheel - Nick at Pelican Parts  
dkennelComments: The Durametric Professional tool not the enthusiast is supposed to allow you to enter PSM bleed mode.
May 9, 2013
 Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help. - Nick at Pelican Parts  
Canadian BoxsterComments: Great article. With my previous 996.2 with PSM I bled the clutch cylinder along withe the brakes. I haven't looked under my 987.2 Boxster S yet. Do you recommend bleeding the clutch cylinder?

What is the easiest way to bleed the clutch cylinder?

Thanks for your help and keep up the great work.

Dave Horner
Nelson. BC Canada
October 31, 2012
 Followup from the Pelican Staff: Bleeding the clutch isn't a bad idea. It's a good way to keeep fresh fluid in the system. The easiest way is to use a pressure bleeder. - Nick at Pelican Parts  
peterbigblockComments: This probably sounds like a dumb question, but in a PSM-equipped car, can one pressure bleed the system to get a brake pedal, go down the street and get your ABS to cycle a few times, then rebleed the system?
March 30, 2012
 Followup from the Pelican Staff: Yes. Just be sure the brakes are functioning after the initial bleed. - Nick at Pelican Parts  
squireiiiComments: Is it necessary to also flush the clutch? Not mentioned here, but it is on another board. I'm considering painting my calipers and would prefer to remove them, and will flush in connection with this project. Thanks for any clarification.
January 23, 2012
 Followup from the Pelican Staff: Bleeding the clutch isn't a bad idea. It's a good way to keeep fresh fluid in the system. The easiest way is to use a pressure bleeder. - Nick at Pelican Parts  
HalComments: I have a 2000 Boxster 'S' and just used the Motive Power Bleeder with Super Blue, it was amazingly easy and fast. I didn't empty the reservoir first so the first right side took some extra time because it had more old fluid to push through but after that each caliper went very fast. The calipers on the Boxster 'S' have an inner and out bleeder valve and I started on the on the outer first always. I bought a liter and used about half to two thirds of it. Only thing I didn't have was a turkey baster to empty the reservoir back to the Max level. This was really easy, no air at all was left in system.
December 17, 2010
 Followup from the Pelican Staff: Cool, glad it went smoothly for you! - Wayne at Pelican Parts 
AJRDDSComments: Thank you for the reply. I appreciate it takes a lot of your time to research these questions and post replies. Allan
July 25, 2010
 Followup from the Pelican Staff: No sweat! - Wayne at Pelican Parts 
AJRDDSComments: I have spoken to other 987-997 owners who do brake flush-brake bleeding at home without the PST2 device, and they do have PSM. They report to me no problems . I have searched other forums and find no mention of the PST2 device needed to bleed brakes with PSM. May I assume that as long as the reservoir does not go dry, there is no way to get air in the PSM valves?
July 23, 2010
 Followup from the Pelican Staff: Yes, I would agree that's a fair statement. If you are performing something like a master cylinder replacement, where a lot of air is getting into the system, then I would think you would need to have the PSM unit bled. But, if you are simply replacing a caliper or brake lines that are downstream of the PSM unit, then I would think that you would be okay. I think it really depends upon the job. For brake fluid replacement, you can probably get away without putting it into bleed mode, but then you will presumably have some old brake fluid stuck inside the PSM unit. - Wayne at Pelican Parts 
dswansonComments: I was getting ready to flush the brake fluid on my 06 Boxster S following a recent track day, but have doubts after reading this tutorial.

I’m confused by the paragraph stating use of a Porsche System Tester 2 is required on PSM equipped cars. I haven’t seen similar warnings in other online tutorials so I’m wondering what happens if I try flushing the system w/o using PST2? Will I be able to replace most, but not all of the old fluid, or is it more complicated than that?

Thanks,
Dan
May 23, 2010
 Followup from the Pelican Staff: The issue is the PSM controller, which is tightly integrated with the ABS system. For cars with PSM (tracking control), they need to be placed into a special "bleed mode" prior to bleeding the brakes, otherwise there is a potential for air to get trapped in the PSM valves and for both the PSM and ABS system to become non-operational. I'm not sure whether or not the Durametric scantool allows you to enter the PSM bleed mode or not. This is not just related to Porsches - it's also the same for the BMWs with all-wheel traction control.

But, if your car doesn't have traction control, then you will be fine. - Wayne at Pelican Parts
 

Check out some other sample projects from the book: 

 

Got more questions?  Join us in our Boxster / Cayman Technical Forum Message Board or our Carrera 996 / 997 Technical Forum Message Board and ask a question to one of our many automotive experts.

Or, see what other questions readers have asked about this article...
 Applies to: 1997 Boxster, 1998 Boxster, 1999 Boxster, 2000 Boxster, 2001 Boxster, 2002 Boxster, 2003 Boxster, 2004 Boxster, 2005 Boxster, 2006 Boxster, 2007 Boxster, 2008 Boxster, 1999 Carrera, 1999 996, 2000 Carrera, 2000 996, 2001 Carrera, 2001 996, 2002 Carrera, 2002 996, 2003 Carrera, 2003 996, 2004 Carrera, 2004 996, 2005 Carrera, 2005 997, 2006 Carrera, 2006 997, 2007 Carrera, 2007 996, 2008 Carrera, 2008 997
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