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jhowell371's Avatar
 
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If the bore is clean no need to hone. It's not like you're seating piston rings. On the other hand if it's corroded just junk it. Honing won't remove pits and I never heard of anyone boring them oversize. Most rebuild failure is caused by rebuilding units that should have been scrapped. In the aircraft field you sometimes have no choice, rebuild what you have as nothing else is available until a similar plane is scrapped or crashed and parts salvaged. Been there done that sometimes even using tractor and vacuum cleaner parts. Keep'em Flying.
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Last edited by jhowell371; 02-04-2018 at 05:54 AM..
Old 02-04-2018, 05:51 AM
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it is actually a lot like piston rings. the slightest anomaly in the bore will wear a spot out the rubber seal very quickly, just as it would with a ring. these tiny little cylinders don't have any room for error. they are holding a lot of pressure over a small area, just like a ring.

clean would have to be defined as shiny, still showing the cross hatch pattern, absolutely no pits, scratches, or bumps, just like a piston cylinder bore.

the problem here is that clutch fluid (unless you are using silicone) is hygroscopic (that means it absorbs water). since these things are almost always cast iron, that means a high propensity for minute amounts of rust. you often can't see it either. if you get in there with any sort of abrasive material, other than a honing tool, you could remove material in an uneven fashion, and then not have a full seal.

this is why you have to flush your hydraulic system every 2-3 years. it generally prevents the rust, and thereby the failures.
Old 02-04-2018, 08:37 PM
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From May 2018 it will be a an MOT failure in UK to have dirty hydraulic fluid showing in the brake master cylinder
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Old 02-05-2018, 06:53 AM
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Sorry Flash, but comparing metal piston rings to a rubber cup is a bit of a stretch even for you. You did however define a clean bore very well. Don't rebuild anything less unless conditions dictate you must. When our seemingly inexhaustible supply of slaves and masters dries up then an overbore and sleeve to save damaged cylinders will be in order as long as the rubber parts are available.
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Old 02-05-2018, 01:17 PM
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not a stretch at all. but for the compression factor, the function very similar. a piston draws in and pushes out. the rings and the rubber cup seal the piston. the problems are essentially the same for both. sure, the materials and how they react to things are different, but that really doesn't matter when it comes to a decision as to viability of rebuild versus replacement. you still need the same condition of the cylinder, for the same reasons, in order for it to work.

Last edited by flash968; 02-06-2018 at 01:20 AM..
Old 02-05-2018, 09:14 PM
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Just yanked your chain for fun Flash, it never fails
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Old 02-06-2018, 04:44 AM
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no worries.
Old 02-06-2018, 05:20 AM
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Quote:
Originally Posted by v2rocket_aka944 View Post
I think I heard once upon a time that the 944 clutch cylinders were remarkably similar to some similar-vintage Mercedes parts (which might be easier to find in your part of the world).

I recall the "main difference" that person noted was the MB didn't have the same elbow fitting for fluid from the brake reservoir.
the one i picked in Beirut and fitted, i was told was a mercedes part. thanks for your help
Old 02-07-2018, 05:02 AM
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Porsche Crest Retainer ring

I bought the FTE kit for my slave cylinder and bought a new FTE master. The rebuild kit I found for the master actually did cost more than a new one. Both the master and slave are built by FTE. I've read in a couple places that FTE is the factory supplier of both parts.

The slave rebuild went very well until the final step; installing the star retainer ring in the end. I spent a solid 45 minutes trying to get it in so it would stay. It wouldn't. Does anyone have any hints or a tool recommendation to get it to say in place?
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Last edited by rbuswell; 07-11-2018 at 11:24 AM.. Reason: line spacing
Old 07-11-2018, 11:24 AM
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Porsche Crest Got it to work ...

Quote:
Originally Posted by rbuswell View Post
... The slave rebuild went very well until the final step; installing the star retainer ring in the end. I spent a solid 45 minutes trying to get it in so it would stay. It wouldn't. Does anyone have any hints or a tool recommendation to get it to say in place?

I ended up bending the tines up a little and pressing the retaining ring in with a long 22 MM socket and a small hammer.
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Old 07-11-2018, 11:47 AM
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