6 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH1998 Porsche 996 Brake Problem
Leading reported evidence
Replace but it doesn't appear
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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Performed · outcome unconfirmed · Original poster
They are now thinking that the vaccum hose needs to be replaced but it doesn't appear to be leaking.
Leading evidence: 'Replace but it doesn't appear' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check carefully' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed
However, your problem began before parts were replaced.
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Suggestion · Original poster
I will check with the garage to see if they tested the Vacuum but I would expect they didn't.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
6 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 1 adjusted by outcome qualification.
2 acknowledgements have no verified action link; they do not establish a repair result.
Help!! I have a 1998 Porsche 996 with a problem with the brakes, they all come on while driving, When I am driving I can feel all the brakes coming on until the car come to a halt, I have worked out that if I detach the booster vaccum hose and reconnect it the brakes are release until they come on again in a mile or two. I have had it in and out of the garage without success, they changed the Master cylinder and brake booster last week but still they problem exists. Now the brake fluid warning light is on and the brake fluid is at max follow the change last week. They are now thinking that the vaccum hose needs to be replaced but it doesn't appear to be leaking. If anyone can help it will be much appreciated because this is costing my loads and I can't see an end to it. Cheers.
So...the car developed a problem with the brakes. "They" replaced every major component of the brake system...master cylinder, brake booster and I would guess also a full bleed of the brake system. "They" did not fix the problem. "They" are recommending replacing a vacuum line. Did "they" do any testing or checking the vacuum? Who is "they"? A Porsche specialized mechanic? Did "they" make sure the replacement parts were OE Porsche parts? I remember one instance where a replacement master cylinder was 1mm off and it did result in problems like you are having. However, your problem began before parts were replaced. Any other work been done on the car lately? Brake pads/rotors...how many miles on those?
Thanks for the reply Joe..The garage is a sports car specialist Porsche, Audi and BMW mainly, I ordered the parts (Master Cylinder and Booster) from Design 911, I spoke to them first to make sure I was ordering the correct parts. I will check with the garage to see if they tested the Vacuum but I would expect they didn't. I took the car out today and after a few miles I experienced the same problem both with the ABS pump connected and again without it connected because I wanted to rule this out especially considering the cost to replace it. The car has done 83k and has been well looked after, basically when driving I notice the brake petal starts to get stiff until its almost solid then following this the car slowly starts to drag, just as those the brake are being slightly applied and this increases as I drive, then by disconnecting the vacuum hose the pressure is release and everything is back to normal and so on. The brake fluid warning light is on despite a brake fluid change last week, according to the reservoir the level is ok. Also since several disconnects of the vacuum hose the emission light has also come on. Brake Pads and discs have only done 8k and were change approx.36 months ago, callipers refurbished about 24 months ago, no brake problem until 6 months ago.
There was a problem with early 996's, 98-99 with water intrusion into the brake booster causing the brakes to not release and bind after hot. A TSB was issued also. There have been other similar failures from the pedal not fully returning to rest and also as Joe stated, some parts(master cylinder/booster/push rod) not having appropriate "free play" between components. This must all be check carefully.
Thanks Joe, The garage is a sports specialist garage mainly dealing with Porsche's, BMW's and Audi's. I have used them for years, so I do trust them to some degree.
I supplied the master cylinder and brake booster, I ordered these from Design 911 UK, I did call them first to make sure I ordered the correct parts and to be honest they were very helpful. I went out in the car again tonight with the ABS fuse removed to confirm this wasn't the cause, alas the same problem, after a couple of miles the brake pedal stiffens followed but the car starting to drag. The only way I can release the brakes is to disconnect and reconnect the vacuum hose. Cheers.
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