I have also had this problem and it always seems to be due to
a very slow leak like you mention.
Also....
> a tight, leak-free system. Even on systems that do not have
> a rubber seal on the top of the fluid reservoir (small
> breather opening open to the air) ......................
> That brings up a point, however. If you have a system that
> exposes the brake fluid in the reservoir to the outside air,
> even if it is only through a small breather opening, you
> should change glycol-based fluids quite frequently, since
> they will absorb more moisture from the outside air than
> they would in a totally sealed system.
The main brake specialist in Adelaide tells me that even on
sealed systems such as you mention there will still be water
uptake in the fluid. He said there has been much debate on the
problem over the years and it has always been blamed on the
breather hole in the master cylinder cap on the older systems.
But when the industry went to sealed systems thinking that
they had licked the problem they found much to their surprise
that it was still happening. He states that it is now
becoming an accepted theory that MOST of the water uptake is
actually through the flexible rubber brake lines from
atmosphere. I suppose this must be something along the lines
of osmosis?
He says that the only remedy is to change the fluid every year
on vehicles that don't see much use. (There are 15 bleeders on
an M8 Greyhound and trying to bleed it any other way than by
pressure bleeder is an excercise in futility).
I find it interesting that my normal car has never demonstrated
any fluid problems, but it see's about 20,000km a year use.
So perhaps heat generated by daily use in the system serves
to force the water back out?
Regards
Doug
+++++++++++++++++++++++++++++++++++++++++
M8 & Other Armoured Vehicles
_______
_/_(_o_)_\_
_/|___|_|___|\_
/ [___] [___] \ Douglas Greville
/\_ [o] [o] _/\ Broken Hill
|w||___________||w| N.S.W.
|w|\u u/|w| Australia
|w| \_________/ |w|
[w] [w]
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