MK1 brake master cylinder rebuild kit?

[Ratkiller]

Does anybody sell a rebuild kit for the original tin cup brake master cylinder? (Can they be rebuilt?)
It's the same size as the cluth master cylinder and as it's original to the car I would hate to replace it with a new bright shinny one.

[Tim]

Seal kits are available from somerford mini, but depending on what is wrong with the master cylinder it may need more than just a kit through it. If the cylinder is pitted they can be bored and sleeved in stainless (or brass), and if the reservoir is damaged they can be replaced with a better one off a later cylinder, to keep the original shaped cylinder.

http://www.somerfordmini.co.uk/eshop/in ... page&id=57

Tim

[Ratkiller]

How do I know whitch bore I have? It's a fairly original 61 delux, non-cooper. So I assume it's either a 75 or 70.

[Tim]

According to somerford it should be 0.75" up until about 1962. What shaped top does it have? I'm pretty sure all the nut top and hex top ones were 0.75".

The only way to be sure is to measure it.

Tim

[Ratkiller]

What exactly do I measure?

[Tim]

The diameter of the cylinder bore. Its a little hard to describe and I don't have access to a decent sectional drawing of the m/c at the moment. You need to have the master cylinder out of the car, turn it upside down, remove the rubber boot that covers the end of the cylinder and measure the bore diameter with a pair of calipers. Its easier with the cylinder disassembled, because that gets the circlip and pushrod out of the way, but you should be able to do it with them in.

On an old m/c there's a fair chance that the bore will be pitted and that a seal kit alone won't be enough to get it right.

Tim

[andy1071]

You will need to dis-assemble the cylinder to measure the bore size.
The end of the cylinder where the push-rod, circlip and washer sit are always a bigger diameter than the bore (so that the washer doesn't drop down and jam).

You will want to take it apart anyway to check the condition of the bore...

[Tim]

Andy is correct, now that I look at the sectional drawing. I've marked what you need to measure.

MasterCylinderSection.jpg

You could try measuring at the very end of the cylinder , if its between 0.7" and 0.75" you'll know its the smaller size, but if its 0.75" or larger you'll have to strip it.

Incidentally, the picture shows an early M/C with the removable threaded top.

Tim