On 23 Apr, 18:21, TD Driver wrote:
I've got a 1952 MGTD. *When I put her to bed last fall, the brakes were
fine. *Now the peddle goes down to the floor. *

That's not good, any brake-related not-good counts as very not good
and needs proper fixing.

You probably don't have a "leak" as such, but rather a failed seal or
cup washer on the master cylinder. If these are old, then they're
likely to be natural rubber and to have failed simply from age.

Your brake fluid (which I guess is DOT 3) has a service life of only a
few years (maybe more in Arizona) and ought to be replaced regularly
anyway. Chances are (on any car I've ever dealt with) it's already
beyond this, so a pre-emptive replacement is warranted anyway. You're
also driving a car that uses cheaper fluid than my car, and has brake
cylinders that are borderline awkward to replace - so replace fluid
before there's any risk of wet fluid causing cylinder corrosion -
that's expensive.

Your rubber flexi hoses to the front wheels and rear axles are also
lifetime limited, and deserve careful inspection as a minimum.

It's also a good idea to inspect the rigid pipes. Replace anything
looking slightly dubious, but there's no need to replace merely on
age.

So I think this is really nature's way of telling you you're overdue a
full brake service and replacement of the rubber parts and all fluid.
Certainly the master cylinder rubbers and front wheel cylinder seals
as a minimum!

Flush the system through and refill with DOT4. This is an improvement
over DOT 3, especially for cars spending a long time in winter
storage, and it's cheaper than DOT 5.1. Performance of any of these
is all you'll ever need for a T-series - you'll fade the shoes long
before the fluid. Don't use DOT 5 (the silicone) as that has some
issues of its own. You can do that, and it avoids much of the moisture
problem in storage, but you should really be putting it into a new or
cleaned system, not filling & flushing.

Fixing brake leaks by topping up fluids is by getting you home from a
desert, not a maintenance strategy. Leaks in brake systems need
attention, no palliative measures.