The ABS brakes on the 80's Benz do feel a bit strange at first -- sorta like Chyrsler power steering in the 60's. You get more braking power by moving the pedal down, but it doesn't feel as if you are pushing harder. Pedal has more travel that a non ABS system, too.

The brakes on both the 300D and the TE feel mushy compared to the brakes on the 280 or the Volvo, but work perfectly.

If the pedal sinks under light pressure or firms up at differenct heights at different times, I'd swap the master cylinder -- cheap compared to loosing the brakes.

Booster being bad will only cause hard pedal.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!