10 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH1999 996 brakes come on by themselves.
Reported or suspected cause
very intermittent
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported cause · Original poster
I forgpt to mention this problem is very intermittent.
Leading evidence: 'very intermittent' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'very intermittent' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Adjust booster master assembly' (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.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed
you describe a classic bad /miss adjusted booster master assembly but you said you replaced them.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
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Performed · outcome unconfirmed · Original poster
I replaced the brake master and booster....adjusted the preload on the rod, etc.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed · Original poster
I replaced the brake master and booster....adjusted the preload on the rod, etc.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
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Suggestion · Original poster
I doubt it, living in Southern California, bit I'm willing to check almost anything.
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.
10 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 · 0 adjusted by outcome qualification.
1 acknowledgements have no verified action link; they do not establish a repair result.
Outcome without a verified action link
No change after replacement of the booster and master.
I'm foreign to these cars....I live most of my life in the 928 world....forgive me. I know I've sinned.
I have a client who has a 1999 tiptronic 996. 145,000 miles.
Driving down the highway at 65-70mph, the car slows down, the transmssion downshifts from 5th gear and the car keeps slowing down....radically. By itself. Very quickly, you find yourself doing 25mph, with the throttle on the floor.
Lifting the brake pedal with your toe (firmly) will cure the problem.
All four brakes come back hot.
I replaced the brake master and booster....adjusted the preload on the rod, etc. Not that.
The brake light switch was funky. Replaced. Not that.
Anyone heard of this problem?
Anyone with clues?
you describe a classic bad /miss adjusted booster master assembly but you said you replaced them. iirc there is no pre-load on the booster push rod to master cylinder. you have exactly the same problems after you replaced the booster ?
No preload. No change after replacement of the booster and master. I've checked this a couple of times....but I could certainly "back it off" some, just to make sure.
I forgpt to mention this problem is very intermittent. Had to drive it 20 miles, today, for it to malfunction.
The only other thing could be the EB adjusted to tight. A slight touching of the rear brakes via a tight EB would eventually heat the rear brakes up and expansion would be enough to slow the car down somewhat to make it change down a gear, but you must have figured that out by now. The EB uses a drum type to hold the car when not moving and not the normal disc rotor. Other than that, I would completely change the brake fluid. Can't think of anything else. Good luck.
i considered that too but he said he has to pull the brake pedal up with his toe [firmly] . he also said all 4 wheels are hot. It still points to a spring in the booster because he has to pull the pedal back up.....over coming engine vacuum .of course this bases on how NORMAL power brakes work the world over...........dealing with a car [po] made by the evil elves in the enchanted black forest who knows how they over engineered it
In an attempt to understand I did a little research. Not the same type of Porsche cars but similar problems. Has something to do with the pre-charge pump on the brake system. You can derive some information from these threads:
https://rennlist.com/forums/996-turb...the-track.html
http://www.6speedonline.com/forums/9...-turbos-4.html
#17 in this diagram -
http://www.autoatlanta.com/porsche-p...section=604-00
The function of the brake system is pretty basic and mostly mechanical, meaning you press on the pedal and it applies hydraulic pressure to the brake calipers. I was trying to find something that would apply to all four brakes and it either has to be the master cylinder or something like the pre-charge pump.
Brake boosters can be bad out of the box. Many folks will chime in about their experiences.
Another option would be what is outlined in Figure 2 here.
http://www.pelicanparts.com/techarti...eplacement.htm
The pedal cluster rod (upper left) must be changed if the booster is replaced with a newer-style one.
Being that your car is a '99, this could be another possible culprit, causing you to not be able to get the adjustment right.
This is a source reference. Confirm exact model applicability in the original material.
