I have a 56 Mercury M100.
I have installed a Volare front suspension and a Ford 9 in rear end.
The power brake booster and master cylinder is from a 88 F150.
Proportioning valve is from a early 80's F100.
My problem is that the pedal goes right to the floor unless I pump it and hold it there.I have bled the brakes several times.
Do you think mayby master cylinder or more air in the lines?It's driving me crazy.
Any help would be greatly appreciated.

 

If you can pump it up and it will stay up then it`s not likely the master cylinder. It would slowly go down as you keep pressure on it with a bad master cylinder.
More likely you may still have some air in the brake system somewhere.
Have you driven it and how long have you had this problem?

 

Havn't driven it yet.Today was the first time I bled the brakes.I did have a few leaks but I fixed them.Just lines that were not tight enough.
I will bleed them again tomorrow.I did not bench bleed the master cylinder before I installed it.However I did go through a whole bottle of brake fluid bleeding the brakes.
I'm also going to try George Moir tomorrow for those Mercury hood barrel clips.He always seems to know where to get Mercury parts.

 

A small fliud leak out can also mean that a small amount of air coming in.

 

Usually when you get brakes by pumping the pedal numerous times the cause is air in the lines somewhere. Your MC should be okay. I will have to tackle a similar problem when I start back on my truck this spring. Mine also gets better when I pump up the brakes but goes to the floor if I don't and I bled them a number of times...even replaced the MC to no avail. Let us know when you get this resolved and what was causing the problem...

 

Thanks for the advice everyone.I'm going to tackle again today.

 

check for fluid leaks but make sure theres no vacuum leaks to the booster