08-22-2012, 11:47 PM
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#1
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Registered User
Join Date: Apr 2011
Location: UK
Posts: 11
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Brakes gone soft?? No brakes?? 986 Boxster
NO Brakes ??
At the weekend me nd my brother replced the top mount bush on the nearside front (UK Right hand drive) Didnt fully drop the hub etc just un done the top 3 bolts and tilted the strut out of the wing to replace.. all was fine until drove it off the ramps and onto the forcourt..
The brakes went soft and need a full pump to the floor before having any brakes??
Sounds like air got into the system but we never opened the lines??
I have now replaced the hard brake pipe from the calliper to the flexi ( it looked as if that could of twisted and deformed so to rule that out I just replcaed it ) and now bled the brakes until there is no air out of that corner.. but still the brake pedal needs pumping until it has bressure?
I have checked to ensure the disc is flush and not pushing the pads back not that
Could the master cylinder just go like that?
PLEASE HELP!!
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08-23-2012, 01:21 AM
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#2
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Registered User
Join Date: Apr 2011
Location: UK
Posts: 11
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What is the symtoms of a failing master cylinder?
what is symtoms of a failing booster? (servo)
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08-23-2012, 03:46 AM
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#3
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Registered User
Join Date: Dec 2007
Location: Seattle
Posts: 735
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The symptoms you describe sounds a lot like a dual circuit master cylinder that has failed on one circuit.
__________________
2000S Ocean Blue Metallic- 116K
3X Water Pump, Clear side markers, Crios Mod, Front engine mount, Flywheel, clutch, RMS, AOS, MAF, serpentine belt, power brake vacuum line, battery, 2X CV boots, Fuel filter, Oil filler tube, 3X ignition switch, 90K service, gas cap
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08-23-2012, 04:04 AM
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#4
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Registered User
Join Date: Apr 2011
Location: UK
Posts: 11
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So I need a new master cylinder?
Thanks for getting bac to me -
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08-23-2012, 04:18 AM
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#5
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Registered User
Join Date: Dec 2007
Location: Seattle
Posts: 735
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Do some more checking before you run out and buy expensive parts.
When I was in automotive school, my instructor said a good mechanic will change what is broken, a bad mechanic will just start changing parts until he fixes it by a process of elimination.
__________________
2000S Ocean Blue Metallic- 116K
3X Water Pump, Clear side markers, Crios Mod, Front engine mount, Flywheel, clutch, RMS, AOS, MAF, serpentine belt, power brake vacuum line, battery, 2X CV boots, Fuel filter, Oil filler tube, 3X ignition switch, 90K service, gas cap
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08-23-2012, 04:25 AM
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#6
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Registered User
Join Date: Apr 2011
Location: UK
Posts: 11
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Sounds a very fair outlook -
So I am a progressive learner.. worked on cars for over 10 year but only had brake issues this once? all other where just a simple case of fitting new pads etc and doing the normal bleeding? at the moment I have a problem and I need to know where to start as a process of elimation into what is wrong by testing?
Thanks
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08-23-2012, 04:05 PM
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#7
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Registered User
Join Date: Dec 2007
Location: Seattle
Posts: 735
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Well, I suppose the first thing to do is to check all four corners for any signs of leaking.
I've never had to test a master cylinder before, they either worked or didn't. I would think that if you disconnected the brake lines from the master cylinder and put in some screwed in plug fittings, and then applied pressure to the brake pedal, it should have a solid pedal pressure since the brake fluid can't go anywhere. If it goes to the floor, you have your answer. Not sure how you would get the plugs in without introducing air in the system, but maybe you could screw them in partially and then bleed the air out like you would with a caliper. You would have to make some sort of accommodation to catch all the fluid that would be spilling all over. You don't want to get it all over the car and ruin the paint.
Someone with more recent experience may want to chime in if my process is flawed.
Edit: I suppose you could remove it from the car and test it on the bench. That way you won't get brake fluid all over the place. If it is bad, then you already have half the job done.
__________________
2000S Ocean Blue Metallic- 116K
3X Water Pump, Clear side markers, Crios Mod, Front engine mount, Flywheel, clutch, RMS, AOS, MAF, serpentine belt, power brake vacuum line, battery, 2X CV boots, Fuel filter, Oil filler tube, 3X ignition switch, 90K service, gas cap
Last edited by Spinnaker; 08-23-2012 at 04:13 PM.
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08-23-2012, 05:44 PM
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#8
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Porsche "Purist"
Join Date: Aug 2003
Location: Wisconsin
Posts: 2,123
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Replace the rubber brake hose and pressure bleed all four wheels.
__________________
1998 Boxster with 7.8 DME, 2005 3.6 liter/325 hp, Variocam Plus, 996 Instrument panel
2001 Boxster original owner. I installed used motor at 89k.
1987 924S. 2002 996TT. PST-2
Owned and repaired Porsches since 1974. Porsche: It's not driving, it's therapy.
Last edited by Paul; 08-23-2012 at 05:47 PM.
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