The rubber bellows looks to be perfect - why would it not seal?
Do both caps have the same thread?
Did they both have the 'paper' washer (not in the parts books) when used?
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Do you mean the original bellows? If so, then I suggest you replace it with the later diaphragm (which must be folded before fitting).
Are they plastic or alloy caps? The plastic ones (which I seem to remember were only fitted to Triumphs originally) seem to be a bit loose on the thread to me, so probably lead to over tightening.I have 2 caps for the Lockheed master cylinder front brake reservoir. One leaks fluid around the edges (down the threads) and the other leaks through the vent hole on top. The rubber bellows looks to be perfect - why would it not seal?
The plastic ones (which I seem to remember were only fitted to Triumphs originally
Thanks L.A.B.And 850 Mk.3 (front and rear) but a different plastic cap.
One is stainless, the other is chromed alloy. Both fit tightly.Are they plastic or alloy caps?
What is the actual purpose of the diaphragm? I don't see it in other applications.
Jaydee
I would wipe the upper side of the diaphragm flange with red brake grease or some brake fluid, and just nip it up.One is stainless, the other is chromed alloy. Both fit tightly.
I wonder if the paper washer keeps the cap from grabbing the top of the diaphragm and distorting it as you tighten?
I agree with the above statement. I do quite a bit of plumbing and there are paper washers used just for that purpose. For instance, on a kitchen sink drain the strainer is inserted through the bottom of the sink with putty around the flange. From underneath goes a rubber washer then a paper washer. After that goes the nut that tightens it all together. If you don’t install the paper washer when you tighten the nut it distorts and will not seal well resulting in a leak. The paper washer allows the nut to spin freely without grabbing the rubber seal and distorting it. Just a thought.One is stainless, the other is chromed alloy. Both fit tightly.
I wonder if the paper washer keeps the cap from grabbing the top of the diaphragm and distorting it as you tighten?