Working on a 37 Plymouth coupe. The brakes worked fine but when driving it the pedal would get higher and higher until the brakes would just lock up. After some research and reading I found the brake pedal needed adjustment to let the piston in the master cylinder come back past the relief port. I did that and got the 1/4 inch free play before the rod contacts the piston. My problem is that now the pedal goes to the floor. I have bled to brakes and am positive there is no air in the system. There are no leaks in the system. I have also adjusted the brakes with the cam bolts until the wheel locks up and then backed them off just until the wheel frees up. Now, short of replacing the master cylinder I am at a loss. Any ideas? Thanks

EDIT>>>>> Just verified... If I adjust the pedal (tightening it up) I get good pedal, but not until after the piston blocks the relief port. Then I am back to the same problem of the brakes locking up after driving a while.

I believe you need to rebuild or replace the master, I suspect the rubber cups have defects or the bore is scored allowing the fluid to bypass the rubber. Gene

look over on the P-15/D-24 FORUM those guys deal with mostly stock 1930s 40s 50s dodge and plymouth,,,they will have the answer,,,

those brakes believe it or not require a special tool to get the shoes adjusted correctly,,,a disc brake swap is super easy to do,,,and make a world of difference,,,just did a 40 plymouth

I agree with fstfish66 about everything he told you you do need a tool to adjust the 39 brakes and chnaging over to disc brakes is easy i just did my 19040 plymouth and they work great

what did cost you?

when done with everything need to complete the swap right around $355.00 when you but the kit you get the mounting brackets all the nuts and bolts you get the spacer for the off set and a space for the stock hub and a parts list of what you need to buy for $155.00 from a site called rustyhope.com the parts list gives you all the NAPA part numbers to finish the job took myself and Fstfish66 about 3 to 4 hours to do the job

I've done several of the Rusty Hope disc brake conversions, I recommend them to many.
Gene

im sure the kit for ur car will be a little different,,the 40 has independent suspension as you have a solid axel,,, the machined parts was around 160 bucks,,,then the cost of rotors,,calipers bearings and seals,, get them from rock auto or your local parts store,,off the shelf parts all part numbers with the kit,,, look for rusty hope or scarebird,,,both guys make kits there are others but way more pricey