Is my Master cylinder bad?

[98SteedaStang]

I just had my rear Brakes pads changed since they were too much of a pain in the azz to do myself. Well after I got the car back the pedal travels to the floor, well almost to the floor. It's not spongy but there is way more travel then before I had the brakes done. I checked the Master and the fluid level is good, I checked for leaks and everything is good. I took the car back and he said it felt ok to him but that my master might be bad. That the masters by-pass valve may be busted. Have you ever heard of this? How much is a new master? Should I check for something else? I tried setting the parking brake. I pumped the pedal slowly for a million times. Anything?

 

[hioc1098]

Have you tried bleeding the brakes? If not, try that first.

Tim

 

[n0v8or]

If there is air trapped anywhere in the system, you can pump the pedal 10 million times and still nothing will change. You are just compressing the air instead of pumping fluid to fill the wheel cylinders.
Your mechanic may have made the same mistake I made years ago, before I learned better. When pushing back the caliper piston to make room for the new pads, either do so very slowly, or better, crack the bleed screw slightly so the fluid in the cylinder is allowed to run out, instead of being forced back into the master cylinder. I damaged my bypass valve the first time I changed pads. Fortunately for me, a new master cylinder only cost $29 in 1982.

Try bleeding the system first.

 

[98SteedaStang]

If there is air trapped anywhere in the system, you can pump the pedal 10 million times and still nothing will change. You are just compressing the air instead of pumping fluid to fill the wheel cylinders.
Your mechanic may have made the same mistake I made years ago, before I learned better. When pushing back the caliper piston to make room for the new pads, either do so very slowly, or better, crack the bleed screw slightly so the fluid in the cylinder is allowed to run out, instead of being forced back into the master cylinder. I damaged my bypass valve the first time I changed pads. Fortunately for me, a new master cylinder only cost $29 in 1982.

Try bleeding the system first.

So you think by pushing back the calpier without opening the bleeder he may have damaged the by-pass valve in the master? So this is something that can occur?