bleeding brakes

the car. a 1979 911 sc
the problem. a leaky master cylinder
the question. can I just bleed the master cylinder after its rebuilt or does the whole brake system need to be bleed ?

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You will need to bleed the entire system, there is no way you will be able to remove the master cylinder without losing some fluid in the lines and getting air in them.


pete

My strong suggestion is to remove all four of your calipers, and completely drain them of old, corrosive brake fluid, then blow out all of the lines to also get all of the fluid out! Inspect the four rubber flex hoses carefully to see if there are cracks or other visible damage. Time spent now may minimize the possibility of more down time to fix other damage in the brake system ... your master cylinder may just the FIRST component to fail ... others may be just waiting for the wrong time to surprise you!!!

There really some very good reasons for completely changing all of your glycol brake fluid every two years as your owner's manual recommeds!


You might want to review the following threads for a similar collection of problems and difficulties encountered:
http://www.pelicanparts.com/ultimate/Forum3/HTML/001122.html
http://www.pelicanparts.com/ultimate/Forum3/HTML/000638.html
http://www.pelicanparts.com/ultimate/Forum3/HTML/000842.html
http://www.pelicanparts.com/ultimate/Forum3/HTML/001230.html


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Warren Hall
1973 911S Targa

Thanks Warren and Pete. Warren you have a good point,I will be checking and changing the old fluid.

Also, I think it is Bruce Anderson that recommends inspection/replacement of the soft brake lines because they can swell and close after many years. For some reason he does not recommend the braided stainless steel upgrade.

Finally, you may need to 'bench bleed' the master cylinder beore putting it in the car. This involves putting it VERY CAREFULLY in a vise. VERY CAREFULLY, since they are soft and can crush/distort. Put hoses on the bleed nipples and the other end of the hoses into the fluid reservoir. Pump, Pump pump until there is no air in the MC. then install and bleed the wholse system starting with the wheel furthest away.

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'83 SC

I think when Bruce's book advised against the SS lines they were generally of variable/questionable quality and sold for "off road use only". The problem is that the braided sheathing can (apparently) rub through the inner teflon tubing and lead to nasty fluid leaks. There are now high-quality DOT-certified SS lines available, and not that I've checked too closely but I have not heard any tales of these failing catastrophically. Surely these new DOT SS lines from Earl's (etc) are far better than 25-35 year old rubber lines in any case!!!

I've had DOT approved Braided SS lines for about a year and 30k now, and I'm extremely hard on the brakes, no problems so far. (and likely every one of you'll hear about it if I do, and manage to survive it...)

I can believe that. I wonder, aren't they a smaller diameter or something? firmer response? They're not expensive.

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'83 SC