Welcome to the forum!

The brake pedal is assisted by vacuum, but if this went out the pedal would be harder to push, as you suspected. I've never had it go out, but I've read that when it does you have to push harder to brake.

I think you're on the right track.

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Ralph

1985 300D Turbo, CA model
248,650 miles and counting...

Thanks for the welcome and thanks for the
reply.

Welcome aboard. There is a ton of great information here and even more very knowledgable people willing to share it with you. I hope you get many years and many miles out of you "new" MB. Great choice!

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2005 Accord Hybrid (Wifes)
1995 Subaru Impreza L AWD (Snow car)
1984 GMC Sierra 1500 (Mine)
1983 300CD Best $ I ever spent. (Mine)
1984 190D (sold and glad I did)
1983 300D (sold and wished I hadn't)

When you press the pedal really fast and hard does it stay hard? But when your gentle just go to the floor?

Good question...........after the "intial" failure, it did re-build pedal pressure.....I believe one time.

Since the first time, however, it now just goes to the floor.

Any fluid loss at all? I had a similar problem in my wagon, it went away after some calipers were replaced.

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

I would first bleed the brakes,you may learn which brakes are getting pressure or not getting pressure,but I am leaning towards master cylinder,let us know what you find,good luck ,AND WELCOME !

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85 300sd SOLD ,85 745i,95 740i,1972 Suburban,1938 International