Q: Brake pedal is going to the floor. Ive changed master cylinder and bled system. No help.

Hi there. Knowing the year, make, and model usually helps us with providing helpful advice. However, I believe I may be of help here. Confirm there are no other brake fluid leaks. Check the caliper slide pins if this model vehicle has a floating caliper design, then see if they are stuck. If they are, the caliper may need to be replaced with the pins. When the pins become frozen in the mount/caliper the caliper cannot move to engage both brake pads and gives a spongy/ pedal to the floor feeling. Verify that none of the caliper pistons are stuck. This will also give a soft/low pedal. These can be checked by simply retracting the piston as per a usual brake pad replacement procedure. If the caliper pistons will not retract, open the bleeder on the caliper to see if the retract with the bleeder open. If the caliper pistons retract with the bleeder open, then the brake line has collapsed. If they do not retract, then the piston is frozen and the caliper will need to be replaced. Also, the proportioning valve could be faulty; I would only replace that if everything else checks okay. If you would like to have this taken care of, YourMechanic has several available technicians that can assist you with a brake inspection and repair.