I would say that you need a new master cylinder to fix your brakes.

On the thumping, it could be axle shaft, flex disc, center driveshaft bearing, transmission mount, or even a tire with a flat spot that gets better as the tire warms up and the pressure increases.

Where are you going to take it for service?

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe