I assume the master cylinder is under the floor. If so yes the residual valves are needed or the fluid can seep back into the M/C. If that happened it would be necessary to pump the brakes for them to work. Are you SURE the M/C has been properly bled? Can you lengthen the rod between the pedal and M/C without putting drag on the brakes? Is the pedal spongy feeling. Does the pedal come up a bit with rapid pumping or does it stay at the same place when pushed hard?

 

as indicated above, residual valves (simple check valves) are required when the MC is lower than the calipers/drums

are you power bleeding them or manually bleeding them?

is the master cylinder properly sized?

what is the pedal ratio? non-powered should be 7:1 or better

 

Bleeding this system has been an absolute nightmare

why not take it to a shop and have them power bleed them?

sometimes having the right tool makes all the difference

 

oh,
I did try to lengthen the push rod, but that locks up the front disc brakes .

 

1) Yes the Master Cyl. is under the floor. ( 7/8")
2) Residual valves, It has 2 lbs for the front's (discs) and 10lb for the rear (drums.)
3) I tried the old school manual bleed... no luck, now i will try my Vacuum bleeder.
4) Pedal ratio, i haven't calculated it, but it looks high, 6-1 or greater.
5) There is a manual proportioning valve on the rears, i have this turned all the way in - allowing max fluid to the rears.
6) when i pump up the brake peddel the peddle does get firmer and has less travel, so im guess air in the lines still ?

 

6) when i pump up the brake peddel the peddle does get firmer and has less travel, so im guess air in the lines still ?

my guess.....yes.

the last vehicle that i bled with a MC under the floor before making a power bleeder required jacking the axles up about 3 feet in the air to get them to bleed. you want the air bubbles to be on a complete upward path to the bleeder or the master cylinder.

 

also,
I did bench bleed the master cyl. no bubbles !

 

Fronts are Wilwood discs, mounted horizontally ( 4 bleeders).

Where does that put the bleeder screws? They need to be above the pistons so air is not trapped.

 

Buy, build or find someone with a pressure bleeder. I believe this what others have called a power bleeder. A pressure bleeder forces brake fluid from a large reservoir through the master cylinder to the caliper or wheel cylinder in a continuous stream sweeping the trapped air with it. My 46 coupe (under floor MC) is almost impossible to bleed without one.

In addition, you will find it to be the best one-man bleeding system you will ever use. Connect the right cap to the MC, put brake fluid in the bleeders reservoir and the MC reservoir, pump up some pressure and go from wheel to wheel. Absolutely works. I can bleed a completely dry system in a few minutes by myself. Probably still a good idea to bench bleed the MC, but I have skipped that step and had good results. Work just as well on hydraulic clutches too.

I've tried vacuum bleeding and the old pump and hold 2 man system. I have found nothing that works as well as the pressure bleeder.

Edit: Of course this will only work if the system is plumbed right to begin with. Like having the calipers mounted bleeders up as noted above.

 

Great input,
I will bororw a buddies pressure bleeder, plus i am going to unbolt the Calipers ( Mounted horizontally) and stand /bolt then up perpendicular to the rotors for bleeding.
hopefully all this gets the air out and i can finally drive the Roadster .

 

How tight are the rea brakes adjusted? They should have some drag on them when turning by hand. You saidif you pump them a couple times the pedal comes up, could ,maybe just need the rears adjusted.

 

I have never seen a pressure bleeder that didn't make a mess. What make/model have you guys used?

 

Dad and I made the one I have. A pile of master cylinder covers and gaskets, a reservoir with a hose on one end and a Schroeder valve on the other

It does leak a bit when you pull the cover off the now very full master cylinder

 

again, why not take the vehicle to a brake shop and let them do it?
its been 2 days, this could have been a simple job done in a few hours.

 

I ran into one car that just couldn't get a firm pedal. I had installed a new master and wheel cylinders, and bench bled the master before installation. I vacuum bled the system, and it still wouldn't get a hard pedal. I finally asked the owner to get in the car and gently push the pedal down as I broke the inlet fitting at the master, and hold the pedal down until I tightened the fitting. Repeated for the 2nd fitting, and instantly it got to a normal firm pedal.
Somehow the lines trapped an air bubble right at the master that I couldn't get out no matter what else I tried. But breaking the lines with pressure on the pedal removed the bubble.