Brake Fluid Level

[fosterfamily]

I've been fretting over a drop in brake fluid level but now wonder if I'm over concerned?
We replaced a wheel cylinder on my daughter's 1969 Minor 1000 a few months back and I topped up the brake fluid to the point where the filler neck meets the main chamber.
Every few weeks it drops by a thimble full and I top up again.
I took all hubs off and inspected brake lines but everything's dry.
The master cylinder is old but the gunk around it looks older still - i.e. no sign of obvious fresh leaks.
I now re-read the manual and it says the level should be 1/2" BELOW the neck.
It goes on to say "The necessity of frequent topping up is an indication of overfilling or a leak in the system which should at once be traced and rectified."
So, it looks like I've been over-filling (but not drastically).
Does the system eventually find it's correct level and I only start to worry if it drops below 1/2"?
Cheers,
Eddie

[bmcecosse]

It doesn't 'eventually find it's own level' - but as the shoes wear the fluid level will drop slightly - especially if you check it AFTER the brakes have been used. There is a residual pressure valve in the system that holds the pistons forward so the shoes are just skimming the drums. Lying overnight they will creep back - so often the first press in the morning is slightly 'long' as the pistons extend - and so the fluid will drop at that time. Let it go down to the 1/2" mark and then keep an eye on it.......