Michael Lytton asked:
> Several weeks ago, I attempted to take my 70B out for a quick spin
> after it had sat in my garage for two months or so. The brake pedal,
> however, failed to inspire confidence by quickly pushing all the way
> down to its stop. After the customary bouncing of the forehead
> against the steering wheel as a gesture of supplication, I checked the
> master cylinder fluid level. There was very little fluid left.
>
> After this, I checked the brake cylinder for each wheel, plus checked
> brake lines under the car. I could find no evidence of leakage. A
> check underneath the master cylinder both in the engine compartment
> and under the dash also revealed nothing.
>
> So can MGB's "use" brake fluid? I must confess I haven't checked my
> brake fluid level in over a year (wince).
As the front pads wear away making the pistons live farther out of the
calipers, the total volume of the brake hydraulic system increases, however,
the difference shouldn't be enough to make your reservoir run dry. I
suspect that this increase in volume is taken into account when a master
cylinder reservoir is designed. Your system has to be leaking somewhere.
If you have a brake booster, the fluid may be leaking from the master
cylinder into it. If brake fluid is leaking from the other end of the
master cylinder, it would run down the brake pedal. Is the surface rust on
your brake pedal darker than the surface rust on your clutch pedal? Also,
when you looked at your rear wheel cylinders, did you pull back the dust
covers on either end to make sure there was no fluid inside the covers? It
takes a while for enough fluid to leak for it to get outside of the dust
covers.
The wheel cylinders are the most likely suspects because they're at the
bottom of the system where water collects because it's heavier. Now that
I no longer anal compulsively bleed my brakes once a year, I've given up
on rebuilding wheel cylinders and just replace them because they're always
pitted from rust by the time they start leaking. However, both the brake
and clutch master cylnders on my car have been there for 15 years.
For the people out there who are compulsive enough to replace their brake
lines, I saw a slick trick on a '67 Cadillac I once worked on. Where the
brake line travelled along the differential, in one spot on the back side
of the axle housing, it dipped below the level of the wheel cylinder. Any
water in the system would collect in this dip instead of in the wheel
cylinder.
BTW, no one is allowed to say anything about 1100's until next Friday
because that's when I'll be back from skiing.
Denise Thorpe
thorpe@kegs.saic.com
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