 Brake Failure, Brake Failure |
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| Rod911964 |
 Dec 1 2023, 01:47 PM
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#1
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Newbie  Group: Members Posts: 12 Joined: 21-December 19 From: Buffalo Member No.: 23,752 Region Association: None  |
914 Brake failure!
Took my 914 1.8 on a 2300 mile rally this past autumn. 914 did great except the brakes went spongy. So I bled the brakes thinking the was air in the lines. Actually bled them 3x. On the way home I had to pump the brakes to get any braking action, ugh! Got home and put the 914 on the lift and started the diagnostic process. Upon the 1st round of inspections… no leaks, reservoir maintains fluid level, no indication of caliper hang up. Took the master cylinder off and disassembled, scoped the bores and found annular rust in the bores. So I figure I’m getting fluid bypass to not hold fluid pressure. Probably the root cause. Then I take the pads out to measure both the rotors and pads to spec. All looks good except for the front left pads. Uneven/slanted wear! (See pics). If I hold the friction surfaces parallel it would mean pistons are cocked. Doesn’t make sense. Or the rotor surface is not parallel. So what causes this situation? Thanks in advance. Rob Attached thumbnail(s) 
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| Rod911964 |
Dec 15 2023, 01:40 PM
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Newbie Group: Members Posts: 12 Joined: 21-December 19 From: Buffalo Member No.: 23,752 Region Association: None |
update to my original question/concern.
I talked to a rebuild tech at PMB Performance about my uneven brake pad wear (see pics). PMB said this is caused by the piston not being clocked properly. So I took the front calipers off and yes the piston had rotated over the anti squeal alignment piece. PMB said the see this all the time. Blew out the pistons, cleaned the pistons and bores, checked the o-rings reassembled. installed a new 19mm MC, bleed the MC and caliper/lines. Oh yea, new pads for the fronts. went for a test drive to bed the pads and test the brakes. The brakes work great, plenty of threshold braking cycles and heat soaks. I still have some "brake job anxiety". What is the typical brake pedal movement before pad engagement? My pedal moves about 1/3 the range before braking action. Maybe I need to bleed the MC and lines again. I'm hopeing for a rock hard pedal at the top of pedal range (like my RSA). Thoughts, suggestions, experiences are appreciated. Rob |
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Posts in this topic
Rod911964 Brake Failure Dec 1 2023, 01:47 PM
Rod911964 RE: Brake Failure Dec 1 2023, 01:50 PM mepstein I don’t know the problem but the rotors have par... Dec 1 2023, 05:40 PM mskala Are the 'piston retaining plates', those 2... Dec 1 2023, 07:02 PM technicalninja I see wear like that all of the time!
Jammed s... Dec 1 2023, 09:04 PM porschetub Pistons won't tip over with pads that thick or... Dec 1 2023, 11:07 PM mlindner I'm with porschetub, wheel bearing bad or not ... Dec 2 2023, 08:39 AM infraredcalvin Yup, looks like simple piston clocking is needed. ... Dec 15 2023, 11:27 PM Dave_Darling A couple of things to try to get a hard pedal near... Dec 16 2023, 01:06 AM
ChrisFoley A low pedal is typical after a caliper rebuild. Th... Dec 16 2023, 06:42 AM mgp4591
A low pedal is typical after a caliper rebuild. T... Dec 16 2023, 10:17 PM |
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