Wondering if anyone has any ideas as to what to try next? I recently bought a very nice 1989 disc brake 2CV which has been dry stored for the past 14 years and , as I expected , had brake issues. Rear brakes were binding badly but pedal sank to the floor , rear shoes were hardly worn (37000 miles) but cylinders were rusted solid so replaced those and adjusted shoes so they just brush the drums. After this the pedal still sank on the first press but all brakes were working evenly , bled them several times with no improvement so suspected the master cylinder , replaced this today but still no change! Pedal sinks but is fine on second press and brakes work ok. Only odd thing is the front discs bind very slightly though the pads can be pushed back ok. Have checked the master cylinder push rod is not too far in , could there be something wrong with the calllipers? No sign of leaks anywhere and fluid level doesn't drop. Any advice very welcome!
Rob

Hi Rob

Sounds like it could be the rear cylinder rubbers retracting the pistons too much. The result is that it takes a pump or two to push them back against the shoes when applying the brakes.

A quick search of threads on here should see this issue documented some more and as far as I remember Ecas do offer instructions on how to trim the rubbers to rectify.

You can use the springs from the rear lights to push the pistons back out. Ken told me that, I think?

Yes that rings a bell!

Sean knows of another (plumbing related?) source for suitable springs, if you haven't got any spare 2CV or Dyane rear lights from which to 'borrow' springs.
As Will has already commented, it's the incorrect shape of the dust covers which is the cause of this problem, nothing to do with hardness or softness of the O rings on the pistons, so re-using the old dust covers is another solution; not too keen on cutting dust covers, I'm afraid...

did you center the rear linings?

yup in side old syphon flush mechanism there is a long (6" at least) stainless spring of about the right dia - some are a bit big. Its not everyone that has a plentifull supply of old Dudley syphon flushes ....but ive 2 in the skip at work that ill try and canibalise them if i get the chance.

Thanks everyone , you were right! Cylinder pistons were retracting away from the shoes , cured with a couple of tail light springs which are a perfect fit. Great forum this!