6 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
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YOUR RESEARCH996 Brake come on by them self after 3-5 miles
Leading reported evidence
Adjust push rod
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
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1
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Performed · outcome unconfirmed · Original poster
I also adjusted the push rod for more lash hoping it didn't have enough adjustment.
Leading evidence: 'Adjust push rod' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Adjust push rod' (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 · Original poster
I also replaced the push rod which threads on to the threaded shaft coming out of the booster
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Suggestion · Original poster
I was told change the ABS control unit, then the master cylinder, and brake booster.
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6 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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1999 996 3.4 all stock.
Went to a DE track event the car ran great. A week later went for a drive and in about 3-5 miles the brake pedal became hard and then I need to pull over the car would not move.
The front brake were locked so I decided to pull the vacuum line from the brake booster, I heard a swish and the brakes released.
Got back home looked over the brakes nothing jumped out at me. Drove the car again same thing happed.
I was told change the ABS control unit, then the master cylinder, and brake booster.
I changed each one then I tested, same result. How much Vacuum should there be at the booster?
Could some shed some light on this.
If you search the archive here you will find your answer...
This specific problem has been covered a few times...It has to do with the push rod length from the master cylinder to the brake booster setting . Several people have went down the same path as you and finally end up fixing the problem of the push rod length...
There was also a TSB issued by Porsche about 20 years ago about water intrusion getting into the pushrod area from the master cylinder to the brake booster with some updated part numbers.
I don't remember the details since it's been many years and my old brain just can't keep up...lol..Good Luck
The archive is your friend !!
One was fixed with new bushings on the brake pedal assembly casing binding of the pedal ( not returning).
One was fixed with NEw TRW brake booster.
One was fixed with TSB new brake booster, booster linkage/pushrod and new part to keep water from getting into the booster ( 99-2000 only)
https://rennlist.com/forums/996-foru...p-1999-c4.html
https://rennlist.com/forums/996-foru...-sticking.html
https://workshop-manuals.com/porsche...modifications/
https://rennlist.com/forums/996-foru...problem-3.html
https://rennlist.com/forums/996-foru...-brakes-2.html
https://rennlist.com/forums/996-foru...hemselves.html
https://www.renntech.org/topic/46145...g-brake-pedal/
I had this same problem on a 986 Racecar I built last year.
Coupe of things.
Booster- could be bad.
In my case, after driving my self nuts rebuilding and swapping calipers and not fixing the issue I found that the pedal mechanism itself was getting hung up- if you pull the brake pedal back manually with your foot do the brakes release?
--Aaron
Thanks for the reply, will check that out tomorrow. I also adjusted the push rod for more lash hoping it didn't have enough adjustment.
will post what I fine out.
Thanks.
UP DATE:
Well went for the test ride same thing, brakes still coming on, tried pulling up on the pedal no movement at all, no release. I also replaced the push rod which threads on to the threaded shaft coming out of the booster
and bolts to the aluminum casted brake bar.
This is the second new bake booster don't think both were bad also master cylinder.
Can't fine in the manual detailed description on how to adjust the push rod? Can anybody help me with this?
This is a source reference. Confirm exact model applicability in the original material.
