Mike,
One supposes that, in a 40 year old master cylinder, there could be a
weak spot. In all likelihood, though, it's one of the rubber seals/cups
that has failed. Why they demonstrate inconsistent leaks puzzles me; one
would expect that they would leak or not leak. Similar to your
experience, I had an MGB clutch cyl that would hold fluid perfectly for
weeks, but leave the car at the airport for five days and the thing would
be drained dry, every time, with a puddle on the pavement underneath.
As part of my annual MGB-GT brake master cylinder replacement
program, I just sent a one-year-old bought-new MC to White Post for
rebuilding. Billy, on the phone, explained that they use new cups and
rubber bits to their own specification, having found that replacement
rubbers are inconsistent in quality. We will know in a week if WP
sleeving and WP rubber bits keep all the fluid in, some of the fluid in,
or none of the fluid in.
Over the years I have bought a number of rebuild kits for hydraulics.
Some of my rebuilds have been perfect; some have leaked. Most shops
won't do rebuilding themselves if new parts are available. One cites
inconsistent performance of the rebuild kits too, and the burden of time
if the rebuilt leaks and the shop has to eat the remove and reinstall
labor, plus customer unhappiness. He also told me that he believes the
WP rebuilts to be better than new. As before, we will know from our own
experience in a week.
Having enjoyed success with WP's work in the past, I think that, in
your shoes, I would remove the MC, send to them, get it back in a week or
ten days, and have peace of mind.
Bob
On Wed, 17 Mar 2004 07:39:17 -0500 "Mike Razor" <mrazor@mis.net> writes:
> The master cylinder on my 59 MGA has dumped out all the brake fluid.
> This happened once last Fall and I refilled it to see if I could
> find the leak, no leak, worked well for the rest of the year. Went out
> about two months ago and it had lost all that fluid, in the engine
> compartment, as during the Fall. It appears to be leaking from the
> bottom, but I can't really seem to find a hole or any fluid around
> any of the fittings. I put a kit in it two years ago, but it was
slowly
> losing brake fluid then, just enough that a small rag stuffed under
> the master cylinder would catch.
> So it seems that it holds the fluid for weeks and then if left to
> sit it drains out.
> Before I drop some big bucks on a new master cylinder, does anybody
> have any suggestions as to how I might find the cause of the leak.
> I am thinking it is in the body of the master.
> THANKS!
> Mike
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