Brake Master Cylinder Overhaul

[weetchus]

Hi all.
Just wanted to ask:
1. if this brake master cylinder looked okay,
2. how to remove the plastic reservoir,
3. if the flange end is meant to have the recess/groove
4. and what gasket/seal do I use for the flange connection. Or can I make one?

Thanks all!

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[jor henderson]

1, looks ok to me, bit rusty but it is the inside that counts
2,the reservoir is removed by knocking out the two roll pins and pulling the plastic straight up
3, no clue what the groove is for
4, I would put a bead of silicone round the outside of flange before bolting to bulkhead

[weetchus]

Thanks Jor. Good advice. Maybe someone else knows what the groove is? I removed a black, old, rotten seal thing from the flange surface... looked like a rubber or maybe even cork gasket? Silocone is a good call.

1, looks ok to me, bit rusty but it is the inside that counts
2,the reservoir is removed by knocking out the two roll pins and pulling the plastic straight up
3, no clue what the groove is for
4, I would put a bead of silicone round the outside of flange before bolting to bulkhead

[weetchus]

Hey Jor.
I can't get the pistons out. There is no circlip as you can see and tapping it face down on wood of from the rear with a rubber mallet is not working. Yet the piston depresses pretty easily when I push it in.
Any ideas?

Part number is NRC6096

1, looks ok to me, bit rusty but it is the inside that counts
2,the reservoir is removed by knocking out the two roll pins and pulling the plastic straight up
3, no clue what the groove is for
4, I would put a bead of silicone round the outside of flange before bolting to bulkhead

[jor henderson]

when you get the reservoir off, in the inlet furthest from the bulkhead, there is a small pin you have to lift out to get the piston out

[weetchus]

Jor, I had tried to take out the two pins (one in each reservoir) but could not get them out with a pair of long-nose pliers.
I tried again, on your advice, and used a small screw to screw into each of the roll pins creating a means to withdraw them both. Once I did this the pistons came out easily and I was able to service them and the outer case. Good thing too as there was a little rust spot at the very back fouling the brake fluid. So I used some emery paper on the end of a dowel to get rid of it on the rust, coated inside with some brake fluid and reassembled. Seals seemed fine.
It's all back together now and should be good.
Thanks for the advice.
Alex

when you get the reservoir off, in the inlet furthest from the bulkhead, there is a small pin you have to lift out to get the piston out

[weetchus]

Here's a pic of it dismantled and painted.

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when you get the reservoir off, in the inlet furthest from the bulkhead, there is a small pin you have to lift out to get the piston out

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[jor henderson]

did you ever find out what the groove is for?

[weetchus]

Apparently it is a drain groove... whatever that means. I thought the idea was to keep fluids inside? Maybe it stops water from collecting in the lower end of the seal and rusting out?

did you ever find out what the groove is for?

[Jon S]

I would guess that the grove was there in the event of any of the piston seals leaking. The brake fluid could then drain out visibly and indicate to the operator that there was a problem. If this happened, the operator may have already noticed that the brake fluid level had dropped in the reservoir during the daily checks, seeing the fluid leaking out of the grove, could cut down on time spent looking for the leak. Just a guess!

Regards