1992 Plymouth Voyager mileage: 90,000. Brakes Not Working - parked my 1992 Voyager Minivan one night and brakes seemed to be working fine. Next morning brake pedal goes to the floor. Checked master cylinder and both reservoirs are empty. See no brake fluid leaks on ground. Have replaced both rear wheel cylinders in last 9 months, one about 3 weeks ago. Have replaced front disc rotors and pads about 3 weeks ago as well. Brakes have been fine since then. Do I have a bad master cylinder or could the problem be something else?
It is possible that you have a bad master cylinder but you should inspect all brake hoses and wheel cylinders as well. Losing all the brake fluid in a short period of time indicates that you definitely have a leak somewhere. It should show up during the check.