My brake pedal is getting soft so I decided to bleed my brakes. Front pads are new and the rear looked very good. So I go to bleed the brakes and the driver side drum brake and the bleeder screw brakes on me. I went ahead and bleeded the other 3 sides but my pedal still goes to the floor. Their is only air bubbles in the passenger rear when bleeding.

So my question is: 1. Is it possible to effectively bleed lines with 3 bleeder
screws?
2. How can I tell if my master cylinder is bad, or brake booster whatever that is?

 

To test the brake booster, pump the brakes while the car is turned off. If the pedal gets stiffer with each pump, then your brake booster is fine.

 

once you get all the air out, rest your foot on the pedal. if it sinks, you will need to replace. it is not uncommon for this to happen.

 

have you checked if your wheel cylinder is leaking??

 

It would be very difficult to bleed all of the air out of the system if you cant bleed one of the wheels.

I have had a mc go bad and it would hardly push fluid to the back wheels. The rear brakes would not work at all just the fronts.