Master cylinder bellows

Stillreel · Mar 20, 2012

I've worked with a few brake fluid master cylinders but I've not seen a bellows in the reservoir before (06-1946). Is this essentially a seal for the cap or does it have another function? The issue is that Walridge doesn't stock them (or at least list them on their website). Can I get away with a good seal at the cap?

BC

303 fmj · Mar 20, 2012

Stillreel said:
I've worked with a few brake fluid master cylinders but I've not seen a bellows in the reservoir before (06-1946). Is this essentially a seal for the cap or does it have another function? The issue is that Walridge doesn't stock them (or at least list them on their website). Can I get away with a good seal at the cap?

BC

yes, it does act as a seal. It also helps to keep the brake fluid from sloshing around and getting air in the line causing a weak braking effect---or worse --no brake at all.

Try some other OEM parts vendors--I think they cost around $15.00 or so.

lbridges · Mar 20, 2012

303 fmj said:
...
Try some other OEM parts vendors--I think they cost around $15.00 or so.

+1

I just picked a rear one up from Commando Specialties on EBay for about ten and shipping. Also was looking through the Old Britts website and I think they had 7 on hand for the front.

rvich · Mar 20, 2012

The cap is vented...It is a really tiny hole, so the bellows becomes important.

L.A.B. · Mar 21, 2012

Stillreel said:
I've worked with a few brake fluid master cylinders but I've not seen a bellows in the reservoir before (06-1946). Is this essentially a seal for the cap or does it have another function? The issue is that Walridge doesn't stock them (or at least list them on their website).

The master cylinder "bellows", part 06-1946 has been superseded by the later "diaphragm" part 06-6032.

http://www.nortonmotors.de/ANIL/Norton% ... 022&Part=9

I suggest you use the later diaphragm as it allows more fluid to be added to the reservoir.
The diaphragm must be folded back into itself when it is fitted so that it can extend if the level of fluid in the reservoir was to drop significantly.

batrider · Mar 22, 2012

Damned amazing how much more fluid fits in the M/C when the diaphragm is properly finagled. Thanks for the picture LAB. I noticed the new rubber was different than the original when installing but never knew you had to do that.

I was goofing around with this last night. The diaphragm has a little tittie sticking up when the rubber is folded properly. This seems to block the vent hole in the cap. Purposely?

Russ

L.A.B. · Mar 22, 2012

batrider said:
The diaphragm has a little tittie sticking up when the rubber is folded properly. This seems to block the vent hole in the cap. Purposely?

I don't think it's intended purpose is to block the hole (and the 850 Mk3 plastic reservoir caps have their vent hole at the side) I think it is there to ensure the diaphragm maintains its correct folded "S" shape.

Master cylinder bellows

Stillreel

303 fmj

lbridges

rvich

L.A.B.

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batrider

L.A.B.

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