Master cylinder

[Alex'n'Ane]

I am fitting disc brakes so need to remove the top hat seal (valve cup) from the new master cylinder i have ordered. In order to not risk damaging the new one, i have decided to practice/ experiment by dismantling the old master cylinder. I have taken out the piston, return spring etc and all down to the valve body. However the valve cup (which needs to be removed) and valve washer are stuck inside the bore and didn't come out when i pushed out the other bits.
I was wondering how you got these bits out? or if they should just 'fall' out with the rest of the assembly?

[DAVIDMCCULLOUGH]

Push a screwdriver in (carefully) from the brake pipe end and it should come out without too much effort.

[Alex'n'Ane]

I had seen reference to just making a hole in the seal elsewhere, and the fact it is called a 'cup' or 'top hat' is worrying me as the piece which i found in the location as specified by the manual is just a thickish rubber ring?

[Alex'n'Ane]

Now all sorted was abit of a pig to get out but all good now hopefully..

[IslipMinor]

Alex 'n' Anne,

The piece that you should remove is the 'residual pressure valve' that sits at the bottom of the master cylinder. It's not a seal, but in the standard drum braked application maintains a low pressure, ~8 lb/in2, to keep the cylinder seals out in contact with the bore and gives a 'good pedal'. Not required, even not wanted, with discs as it then keeps the pads in contact with the disc - definitely not a good idea!

[Alex'n'Ane]

The piece sits just inside the valve cup right, at the end of the spring? And its not at the end of the master cylinder, there is a rubber washer at the end, which is where there was initially confusion.

[IslipMinor]

Yes, the 'Valve Cup' is the bit to remove, and it fits inside the 'Valve Body' - the attached picture shows it.[frame][/frame]

[Alex'n'Ane]

Glad, i did it this morning Fitting the remote reservoir when it arrives, then the new brake lines etc.