strange leaking master cylinder, R1100RT

kennyc · Jul 25, 2014

I have just returned from a trip to the Alps (and this time didn't need to rebuild the FD!) on the second day the bike was left in the sun and the air temp went up to 37C, when I returned to the bike I noticed drips from the master cylinder, I cleaned it off and swore a little, and rode on, I have kept an eye on it over the last 8 days and it only leaks when hot? I rebuilt the cyinder with a new piston kit around 2 years ago, is it worth rebuilding again, or should I resort to cold weather touring?

Smug · Jul 26, 2014

Was the banjo bolt not tight enough or was it leaking from the piston?

Bin Ridin · Jul 26, 2014

Had similar leak on r1100rs in pyrenees 10 years ago. I read that when you pump the master cyl to bleed the system, you can damage the seal in a worn unit by sending it into the unworn part. Likewise, a repair kit does not always last long for same reason. Even honing the cyl is not the full answer, seemingly. Low mileage secondhand one from breakers?

kennyc · Jul 26, 2014

the leak was from the piston, and I honed the cylinder, I was trying to avoid the cost and hassle of a new/secondhand master cylinder as they are not particularly cheap, although neither is a rebuild kit!

Bin Ridin · Jul 26, 2014

If I was doing it now, I would fit the new kit and bleed it without stroking the piston in deep to the cylinder. Maybe by vacuum or by filling from bleed nipple.

GADGET · Jul 26, 2014

I'm no expert here, when you say you 'honed' the cylinder' I thought the cylinder was plain alloy, which I think was the problem with the early model, as they corroded, I believed they resolved this by anodising. If it were me and I was in the same situation once, as brakes are a safety issue, I'd bite the bullet and pay the £100 or so for a new assembly.

kennyc · Jul 26, 2014

GADGET said:
I'm no expert here, when you say you 'honed' the cylinder' I thought the cylinder was plain alloy, which I think was the problem with the early model, as they corroded, I believed they resolved this by anodising. If it were me and I was in the same situation once, as brakes are a safety issue, I'd bite the bullet and pay the £100 or so for a new assembly.

if it was £100 then I would agree, check out the cost! this is a reservoir weep, the level barely drops and the pressure side is not affected, obviously if it was spurting out everytime the lever was pulled then that would be different.

strange leaking master cylinder, R1100RT

kennyc

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Smug

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Bin Ridin

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kennyc

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Bin Ridin

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GADGET

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kennyc

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