1975 Buick Regal's brake light goes on until you 'pump' the pedal once
or twice, then I hear/feel a thump and it goes off. Feels like the
vacuum seal isn't happening? I replaced the rubber inside the brake
fluid cover, as I was told it was the problem, but the light still goes
on, etc. Any ideas? I'm taking it into the shop this week, but I'd like
to hear the ideas here as well. Thanks!

--Tazzy Gal