XJ6 Series 3 Master Cylinder

Has any member here replaced the series 3 master cylinder with any other car’s master cylinder?

What other car’s master cylinder can fit the series 3 directly without issues?

Please help.



Fittings are metric, there are differences between LHD and RHD, some have their old ones machined, I simply put in new rubber; someone has found a GM part ( @ronbros?)


just to get your point: why the hassle? SIII LHD master brake cylinders are around at reasonable price and there’s no gospel I’m aware of that the originals are sub-par. Do you have any particular reason to pick the cherries in the neighbor’s garden?



75 XJ6L 4.2 auto (UK spec)

That MC is using a remote reservoir (S1 or S2). The S3 MC has an integral reservoir. Not sure there’s room on the S3 bulkhead to fit a reservoir.

Yes I know. I personally would use a S3 master cylinder again or refurbish the old one, but I did the research as I didn’t find an affordable new RHD one at the time.
There should be plenty of room left or right of the cast aluminium pedal box and it sits as high as earlier versions, but thankfully the reservoir isn’t aging badly and the master cylinder can be repaired and is still available.