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Senior Member
Join Date: Feb 2000
Location: Lacey, WA. USA
Posts: 25,308
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Brake MC
I don't hear much about brake master cylinders going bad on SCs, and I especially have not heard about vacuum boosters getting destroyed by leaking MCs. On the other hand, this may be a problem plaguing us without our knowledge. I imagine that vacuum booster units for our cars are spendy. I am therefore considering a new MC even though I don't know whether mine is bad or not.
Comments please.
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Man of Carbon Fiber (stronger than steel) Mocha 1978 911SC. "Coco" |
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10-15-2002, 12:23 PM
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If it ain't broke why fixit?
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Bill Verburg '76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone) | Pelican Home |Rennlist Wheels |Rennlist Brakes | |
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10-15-2002, 01:44 PM
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Senior Member
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Location: Lacey, WA. USA
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Well that's my point. It may be broke, and no one knows it. Yet.
I have seen quite a few corroded brake boosters. If our master cylinders are leaking past the seals, then that brake fluid is collecting in the bottoms of our brake boosters. Over time, this makes the brake booster into junk. I just checked it out. A booster is just over $300. A brake master cylinder is under $100. Anyway, I was just wondering if anyone has ever had a booster go bad, and had to replace it. Anyone?
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Man of Carbon Fiber (stronger than steel) Mocha 1978 911SC. "Coco" |
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10-15-2002, 01:59 PM
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Location: TX USA
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If you do not yet have a problem with a rapid drop in the brake fluid level for one circuit, then you don't have damage to seals and cups from corrosion and pitting of the master cylinder cast iron bore ... so, the master cylinder would be a good candidate to rebuild at a significant savings over a new unit! Rebuilding the master cylinder and calipers every five years or so is one way to assure a troublefree braking system. The use of liberal amounts of Dow Corning 4, 111, or 112 on the cups and seals when replacing those parts ... assures maximum lifetime for those rubber parts!
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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10-15-2002, 03:35 PM
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Senior Member
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Wisdom. I know it when I see it.
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Man of Carbon Fiber (stronger than steel) Mocha 1978 911SC. "Coco" |
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10-15-2002, 03:56 PM
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Location: Great NorthWest
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Good thread Super. My '69 and '70 Mercedes coupe/sedan both experienced booster meltdown. You can rebuild these units (they are HUGE) or pay the $675.00 to replace them. One was so bad the only recourse was to get a new one.
The core I got for the old one was over $150.00!! That tells you something about their worth. In all events, is there a rebuild kit for our Porsche MCs? John
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'78 Targa in Minerva Blue |
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10-16-2002, 06:49 AM
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John,
Raybestos still lists kit MK670 for SC/Carrera master cylinders w/ booster: http://www.raybestos.com/catalog/parts.cgi?make=540&make_name=PORSCHE&model=120&model_name=911SC%20incl.%20Carrera&fromyear=1983 In my experience, all Raybestos kits for VW, Porsche, BMW or Mercedes contain a genuine Ate kit still in its' original blue box!
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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10-16-2002, 10:48 AM
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Senior Member
Join Date: Feb 2000
Location: Lacey, WA. USA
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Oooo. That's more good information. No wonder I like you guys.
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Man of Carbon Fiber (stronger than steel) Mocha 1978 911SC. "Coco" |
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10-16-2002, 01:28 PM
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1976 Porsche Carrera 3.0
1995 Porsche 993 Carrera Coupe
