Re: Why do I keep destroying O-rings?

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <365A3A68.B3A73D72@one.net> "Theodore R. Harlan" writes:

> I'm very, very distraught.
>
> I am trying to rebuild the right rear brake caliper on the 90 cq. The
> piston is a Girling screw-in. Every time I screw the piston in, I take a
> half-inch notch out of the o-ring that rests in the cylinder groove. I'm
> not completely severing it. This is before any hydraulic pressure is
> applied. And on the three rings I have used, the notch is identical!
>
> I have absolutely no idea why!
>
> Thing is, the piston is as smooth as glass. Really smooth. And I'm using
> buckets of brake cylinder paste.
>
> My only two hypotheses:
> 1. There is a microscopic imperfection on the cylinder.
> 2. The friction between the cylinder and the ring is sufficient to take
> a chunk out.
>
> These hypotheses seem incorrect. Am I missing anything?
>
> A bad batch of rings? Any way to buy these rings at a lower cost?

Neatly chops out a quarter or so of the inner circumference?

If you're using kit # 443 698 671 then yes - I suspect a bad batch of
rings.  Compare the colour codes on the new and old rings, and check
the diameter compared with an old ring.  "Verfall" is "09/02" on
my kits - I suspect manufacture during September 1998.

Exactly your problem occured to me last week.  I refitted the old seals
and started escalating the problem with Audi.

--
 Phil Payne
 Phone: 0385 302803   Fax: 01536 723021
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