Series 3 persistant brake issue

hi, a mate of mines got a series 3 non servo 88" with new master cylinder and new slaves on all round and all fully adjusted.

The issue is that no matter how many times you pump the brakes you dont get a solid pedal ( or anything near) then when the pedals released the fluid level rises back up along with lots of foam and bubbles. all brake nipples have been bled about 5 times pretty much replacing the entire system of brake fluid each time. no brake lines are wet and any slightly worn pipes replaced.

what are we missing?!?!?!? this problems been going on going for weeks now rendering the series immobile.

help!

buggered seals in master cylinder,which can be caused by aggresive pumping while bleeding

master cylinder was only fitted today?

when you pump pedal are you getting air or splashing in reservoir

air and foam no splashing

have you got any amout of fluid out at wheel cylinders but does sound like masters sucking air on return which could be seals or pipe union/s at master not sealed you can isolate cylinders by clamping flexis ,because its new doesnt mean its allright

got fluid at wheel cylinders. would that explain it filling back up with fluid when you stop pumping as well then? will take master off and take it back to get a swap

its obviously sucking air in on relesae of pedal as well as sucking fluid from reservoir,either thats pipe ends/ unions or seals in master

i would rule out every wheel 1st so clamp the flexi lines 1 by one until you get a firm pedal if you don,t get a firm pedal then it is the master for sure.
i remember i had a similar problem years ago when i swapped out the master cylinder,basically when i adjusted the rod from the master cylinder to the pedal i didn't give it enough travel so it did'nt allow the cyclinder to fill properly-basically just pushing fluid back and too.

This is what an old lad told me to hold pedel down with a bit of wood over night