[968Syncro]

I had the car in at a shop today for some service / repairs. Actually a really good buy, for $269.xx I got 3 things done which eliminated the need for me spend hours to jack the car up, get on my back, go get parts, probably buy a tool or two, swear at the cat, break something, and -- give up and finish the next weekend.



One thing I had the brake fluid flushed, and the owner suggested the brake master cylinder may be getting weak -- there was no significant evidence, just a suggestion. It might have been an upsell, I have no big problem with that, some owners might say great idea let's replace it as preventative. But I figured I'd give it some time first.



Anybody have an idea on the failure rate of brake masters on our cars? Any experiences? I am sure they will wear, but how many miles do you think we have?



Thank you!

Roland

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[94SilverCab]

I had the Clutch hose replaced with the S/S line. Shortly thereafter the Master and slave gave way so they were both replaced. I would not be surprised to find that they fail without the S/S lines as well.



Jay

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[flash]

all of the original hydraulic rubber components are well past their lifespan. i would not be surprised if many have failed.

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[94SilverCab]

I re-read my original post, I did not mean to imply that the S/S line caused the failure, only that the pressure through that system is fairly high.



Jay

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[flash]

yeah - hydraulic systems will seek the weak link. if you don't change them all in that system, you stand a pretty high chance of blowing the one you didn't change.

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[MB968]

Especially on older cars, where some silt may have built up on the inside of the cylinder, it is easy to cause the master cylinder to fail. The old technique of pumping the brake pedal while opening the bleader causes the piston to travel over parts of the cylinder that normally sees no seal wiping. This can easily cause the seal to fail. It is not a guarantee, but I've seen it happen right after someone bleeding the brakes. Just one more reason to use a pressure bleeder.

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[flash]

yup - having had to deal with british sports cars for so long, i had the unfortunate opportunity to see just about every type of hydraulic failure

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[94SilverCab]

Bleeding the clutch is complete PITA, with or without the pressure bleeder. Enlist someone to pump the clutch while you're bleeding the line. (That was my job at RSB).



Jay

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[flash]

nah - it's really not that hard. the only tough part about it is trying to do it in a hurry, or if you didn't change everything all at the same time.



of course, you do have to make sure the little wall that separates the clutch part from the brake part doesn't give you grief and let the clutch area run dry. it's also a lot easier if you actually follow the instructions on the bleeder, and put fluid in the thing. most shops won't do that though, because it wastes a LOT of fluid, and that adds up over time, when you are doing a lot of cars.



i have yet to need an assistant in order to get it right, and i've done quite a few now. i've also never had to "pump" the pedal at all.

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[MB968]

I'm with Jay, mine was a b to get bled. I even raised the rear of the car, never let it run dry, put fluid in the bleeder tank, etc., etc. In spite of all this it took a lot of time and running a lot of fluid through before it was properly bled and I had a functional clutch. Never spent that much time/effort bleeding anything.

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[flash]

maybe not enough pressure in the bleeder, or a sticky bleeder screw? they do tend to get gummed up with gunk, as the rubber cap is often missing.

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[JWahlsten]

Back to the original topic...



I have seen a number of brake master cylinders fail on these cars, but not really on street cars. On a car driven on the track the pressure will build up with the heat and you'll get the reservoir overflowing slightly. Seen it a few times, and have had it myself twice on two different 944 variants.

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