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Old 03-15-2017, 11:41 AM   #1
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Porsche dealership want $2,300 wants to replace brake booster and master cylinder

So, my brakes are doing this thing where the pedal becomes rock hard after a few miles and completely locks up, rendering the car undrivable. I have to wait an hour or so until the brakes go back to normal.

Porsche dealership says it's *MOST LIKELY* the brake booster leaking onto the master cylinder and they want $2,300 to fix it which sounds insanely high because I went onto youtube and found THIS VIDEO where the guy made replacing those parts look fairly simple.

I'm wondering if I should try this myself or take my car somewhere else, but I'm worried about the dealership's diagnosis because they said they weren't completely sure until they dove into it. I'd hate to replace these parts and have the problem persist.
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Old 03-15-2017, 11:46 AM   #2
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Are you losing brake fluid (is the level is going down in the reservoir)?
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Old 03-15-2017, 02:45 PM   #3
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Quote:
Originally Posted by 99 Boxcutter View Post
So, my brakes are doing this thing where the pedal becomes rock hard after a few miles and completely locks up, rendering the car undrivable. I have to wait an hour or so until the brakes go back to normal.

Porsche dealership says it's *MOST LIKELY* the brake booster leaking onto the master cylinder and they want $2,300 to fix it which sounds insanely high because I went onto youtube and found THIS VIDEO where the guy made replacing those parts look fairly simple.

I'm wondering if I should try this myself or take my car somewhere else, but I'm worried about the dealership's diagnosis because they said they weren't completely sure until they dove into it. I'd hate to replace these parts and have the problem persist.
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Old 03-15-2017, 03:13 PM   #4
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You need to diagnose what is wrong first not just replace everything and certainly this is an easy do it yourself with basic tools and not a $2300 job. A very hard brake pedal, works at first and then gets hard, is often a problem with the booster and not the master cylinder. It is possible that it is just the check valve since you have brakes at first. Never messed with the booster on the Boxster so I don't know where it is but I am sure someone here does.
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Old 03-15-2017, 03:29 PM   #5
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Are you losing brake fluid (is the level is going down in the reservoir)?
Perfect question!! Your booster will not leak into the MC. Your MC will leak into the booster.

I have not had this issue with my Boxster. I have had it with my 30+ year old Alfa Spider.

My symptom was slightly different. I would not have any power assist to my brakes when starting my car. After the car built vacuum, I did have boost. Eventually, over a few years. the problem got worse and I noticed low level of fluid in the MC. The leak got bad enough that I new I had to replace the MC. I also found to about where my fluid was going and I ended up replacing the brake booster at the same time.

Again, I would experience lack of power assist. My brakes did not lock up. Brake systems have not changed much over the years but your Boxster has ABS while my older car did not. ABS is suppose to keep brakes from locking up but I have no idea what their failure mode is.
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Old 03-15-2017, 03:43 PM   #6
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The next step is to read the ABS codes.
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Old 03-15-2017, 06:05 PM   #7
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Guys, a leaking master cylinder will not cause a stiff pedal but rather a spongy pedal. His issue is in the booster or the check valve. No abs codes for that or the dealer would have mentioned replacing that as well.
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Old 03-15-2017, 06:22 PM   #8
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I've never known a failing booster or check valve to lock the brakes....I'm assuming "completely locked up" means the car cannot move.

Read the codes. I'm assuming from the OP's post that he has called the dealer and has not taken the car in yet.
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2001 Boxster bought new. Installed used motor at 89k.
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Owned and repaired Porsches since 1974. Have driven them all the way the Dr intended...

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Old 03-15-2017, 07:25 PM   #9
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Occasionally I go to Renntech.

One of my '99s had a brake pedal that started to stick. Sometimes I had to pull it up with my toe to fully release the brakes. Not the same problem, but it led me to a couple good threads on Renntech.org.
This one seems to be the one for you:
https://www.renntech.org/forums/topic/42415-replaced-brake-booster-causes-grown-man-to-cry/

Here's the DIY thread that I found and fixed my problem with a booster from my '01 parts car:
https://www.renntech.org/forums/topic/15633-brakes-not-releasing-sticking/
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Old 03-15-2017, 08:12 PM   #10
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The most obvious cause for a hard pedal is simply not enough vacuum. Any brake booster requires a minimum of 18” vacuum to operate efficiently. Anything less than that will contribute to the pedal being harder to push. Check the vacuum hose to the booster.....Could be leaking!
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Old 03-16-2017, 02:16 AM   #11
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The most obvious cause for a hard pedal is simply not enough vacuum. Any brake booster requires a minimum of 18” vacuum to operate efficiently. Anything less than that will contribute to the pedal being harder to push. Check the vacuum hose to the booster.....Could be leaking!
It is not unusual for these cars to collect water in the brake vacuum booster which then rots out the metal vacuum housing.
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Old 03-16-2017, 03:44 AM   #12
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I've never known a failing booster or check valve to lock the brakes....I'm assuming "completely locked up" means the car cannot move.

Read the codes. I'm assuming from the OP's post that he has called the dealer and has not taken the car in yet.
We read his post and understood it different, I read that his pedal locks meaning impossible to push, you read that his brakes lock.
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Old 03-16-2017, 05:48 AM   #13
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78F350's post nails it. Bleed the brakes. The dealer is likely correct in suspecting a leaking master cylinder which can leak into the booster.
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2001 Boxster bought new. Installed used motor at 89k.
1987 924S . 2002 996TT. PST2
Owned and repaired Porsches since 1974. Have driven them all the way the Dr intended...

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Old 03-16-2017, 07:53 AM   #14
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Sounds good to me. Where do I find one of those?
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Old 03-16-2017, 07:57 AM   #15
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I've never known a failing booster or check valve to lock the brakes....I'm assuming "completely locked up" means the car cannot move.

Read the codes. I'm assuming from the OP's post that he has called the dealer and has not taken the car in yet.
I took the car to the dealership. It's still there. Should I ask them if there's any codes?
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Old 03-16-2017, 04:22 PM   #16
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No need, I'm pretty sure they did that already.
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2001 Boxster bought new. Installed used motor at 89k.
1987 924S . 2002 996TT. PST2
Owned and repaired Porsches since 1974. Have driven them all the way the Dr intended...
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Old 03-19-2017, 06:52 AM   #17
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You don't say the year of your Boxster. The pre 2000 cars had an issue with water getting into the booster and rusting it out. Water would get into the rubber bellows between the bulkhead and the booster. I had this problem on my 99. You have to drain the brake fluid completely, remove the master cylinder and the booster. I chose to replace the booster and the master cylinder while I was in there. I also purchased the retro fit kit from Pelican so I wont have this problem again. I would say it is impossible to successfully do this without having the Porsche TSB and you must follow it step by step! also, instructions would have you replace the aluminum bar that connects the brake pedal to the booster. I did not do this there are ridges on both sides of the rod that the bellows fits into I got my dremel and machined the ridges off because the ridges are not needed with the retro kit. basically the retro kit isolates the brake pushrod from the bulkhead to the booster so no water will ever get in. I found my brakes locking up at red lights I have a tip and there was no creep found with an automatic. I disconnected the vacuum hose to the booster and stuck my finger in and found the water. PM me if I can be of any help.
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