[Caddylackn]

The master cylinder piston seal is done, and/or the bore is pitted. It is getting really hard to find rebuild kits for master cylinders. I would buy a rebuilt one, but don't trade your original in for a core until you get the new one working.

Brake fluid absorbs water from the air and since the brake booster is not sealed the brake fluid and moisture in the air will soon rust out your brake booster inside walls so replace this asap and flush out the existing brake fluid out of your booster.