Hi I bought a re-built clutch master from AUS. It leaks at the bottom from the joint of the reservoir and the main body of the master cylinder how do I fix that leak?

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1973 Clubman GT
"Never ending project”

If the leak is from the body to reservoir join (plastic to metal) then if the bolts are tight enough, the rubber seal / oring may be damaged or missing.

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Cheers Dave.

As Steam said, and just got in ahead of me, it may need replacing, or just nipping up the two screws.
It is available as a part: see

https://minisport.com.au/prod2660.htm

It can be replaced without having to bleed the clutch hydraulics.

Thank you both. I have tightened the bolts a bit but still leaks so it must be the o-ring I never inspected it after I bought it I assumed it was RTG. Thank you

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1973 Clubman GT
"Never ending project”

Does that o-ring stick out much from the plastic housing? I took it out and seems like it barely sticks out of the plastic housing. I can not crack the plastic from over tightening because of the metal sleeves that will stop the bolt from cracking the plastic Correct?

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1973 Clubman GT
"Never ending project”

The seal doesn't protrude very much: this one has been used but is the same thickness as a new one at 5.75mm.

I know there doesn't look like a good seal but I've never had one leak.



You are right about the little crush tubes stopping overtightening.

The o-ring seal is not part of the pressurised section of the braking system as the fluid is gravity fed from the reservoir to the master cylinder itself. As such its function is fairly simple.

I would check that the surface it mates to on the master cylinder is flat with no imperfections that could provide a path for the fluid. Maybe the o-ring is undersized or defective and not providing a flat seal.

Also check in case the aftermarket plastic reservoir has a hairline crack that's not obvious, maybe along the seam.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Got it I put it back and tightened it a bit more now knowing that I can not crush the plastic. I will see if it still leaks if it does I will check your suggestions. The surface it mates too is clean

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1973 Clubman GT
"Never ending project”