Master cylinder connection

[Johns327]

For the CPP 1” bore does it matter if the connection closest to the mounting flange is connected to the rear brakes?

I have a new install and am trouble shooting a dragging brake issue. (4 wheel disks, 1955 2nd series under floor mount). When I loosen the line at the master cylinder the pressure drops and the front wheels turn freely but I have connected the front brake line to the connection closest to the flange. I’d like to know if that matters before I start bending new lines. Everything is new, I even pulled the master out today and pulled the guts out and mad sure it was all clean with nothing in those pressure vents.

My next test will be to leave the lines connected and loosen the master from the booster. My pedal seems to have free play but maybe there is something in that booster that is holding the plunger in. The instructions I have read say to adjust those depths, but not how.

Any help will be appreciated this is driving crazy.

[Black_Sheep]

Your pushrod from the booster to MC might be too long. This gauge from Baer Brakes makes it very easy to diagnose.


https://www.youtube.com/watch?v=8QO2wof4Y1Q

[Johns327]

Thanks I will go and check that today, my guess is you are correct.

The other part of this question does it matter what connection does the front brake connect to. Both reservoirs are the same size is the flow rate from the two ports the same?

[1project2many]

If the bore for the front and rear pistons is the same size then either one will activate the rear brakes with similar force. If you have disc front and drum rear I believe it is better to connect the front brakes to the front port. The tandem master cylinder doesn't apply significant pressure to the front port until the rear chamber has built pressure. Connecting front brakes to rear port applies front brakes slightly sooner and generally builds pressure faster to apply rear brakes.

[dsraven]

first check all the linkages to ensure free travel and no sloppiness. check to ensure there is a return spring to bring the pedal back up all the way.
next check for pushrod free play to ensure the master isn't being held with brakes slightly applied.
check to see if there is a residual valve built into the master and also an inline one. too much residual valve pressure will give you problems.

try bringing the pushrod travel to an extreme so there is for sure free play, then apply the brakes and ensure the pedal comes back all the way. now check if the brakes are still applied slightly. if so then it isn't the linkage so it must be hydraulic. start checking for the proper port for each line etc. if it is easy to see inside the reservoir you can check if the piston is returning all the way by looking inside the res when the pedal is pushed. there should be a little fountain of fluid right when the pedal is pushed, then the fountain goes away as the pedal is pushed further. this is because the master cyl piston travels back further than the supply holes in the cylinder bore so that fluid can return to the res ( from heat expansion for one reason) and also so fluid can flood the piston bore when the brakes are released or pumped. when the pedal is first pushed there is a slight time when the piston hasn't gone past the holes so a little bit of fluid "fountains up" in the res. this is the tell tale to see if the piston is returning all the way back enough.

[Johns327]

Thanks all.
Found my issue with the draggy brakes. There was this dust cover on the master that was holding the piston from releasing pressure.
As far as which of the two ports I went ahead and swapped them. Now the port closest to the flange is connected to the rear brakes.
Mostly YEAH the brakes are acting correctly, now on to steering!