master cylinder pressure switch thread size.

[dmachura]

Does anyone know what the thread size is for the pressure switch in the brake master cylinder found mine leaking over the winter. I just want to to plug it off for now.

[john 215]

Hi,

As all the other fittings on the master cylinder are metric, I would guess 10mm ??? 11mm is a unusual thread size and its not 12mm. Plus during manufacture it would be cheaper if all threads would be same size.

Cheers John

[Beans]

If the pressure switch underneath the master cylinder is leaking there's something wrong inside (worn seals) that needs investigating

[saabfast]

As Beans notes, if there is leakage there the seals on the auxiliary shaft have gone. The switch is not pressure but for brake failure and should be dry. IIRC the switch pin sits on a 'bump' in the shaft which holds it open, and the shaft is static as long as there is pressure on both circuits. If one side fails (big leak) it moves and the switch pin moves off the bump and makes the contacts showing a warning light - by which time you probably know there is a problem! Good luck getting the shaft out for rebuilding, mine was completely frozen in and after more and more brutal attempts I gave in and bought an uprated MC and servo unit.

[FI Spyder]

Because the shaft is dry it tends to seize up. Mine was too but I was able to free it up with a screw driver acting on the cam surface of the shaft. When I overhauled it I put red rubber grease on all the rubber seals and greased the bores.