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  View original topic: 1967 dual circuit MC reconditioning - but how can this work?
Peter - Belgium Mon Jan 11, 2021 12:46 am

Hello all,

I took apart a 67dual circuit MC and cleaned all + reassembled but when fitted to the bus I saw 2 issues:
1/ no oil reached the rear cilinders (not expected)
2/ some oil leaking out from the front of the pump (expected)

when I took it apart again and mocking up where the seals end i wonder how oil can actually get behind this one to be pushed to the rear wheels. The seal seems to be right below the oil passages not allowing oil to flow?




As for teh leak at the front of the MC, that seal is really worn. Any idea if there is a source for these seals? Tthe others could do with a replace as well I'm sure:

Or any other - cheap - MC I can take these out from?

Thanks!
Peter

ToolBox Mon Jan 11, 2021 10:50 am

Do you have a local seal house in your area? I work on brake test machines and our masters are much larger. I use a local seal warehouse to get replacements when needed.

The fluid flows through the body and pistons through machined passages. There is a cutaway in the Bentley that shows it.

Alan Brase Mon Jan 11, 2021 4:37 pm

Wow, you just need to purchase a repair kit for a 1967 cylinder. I suppose the individual parts are available, but a kit will have new pistons in it as well as the brass check valves.

ToolBox Tue Jan 12, 2021 10:25 am

Alan Brase wrote: Wow, you just need to purchase a repair kit for a 1967 cylinder. I suppose the individual parts are available, but a kit will have new pistons in it as well as the brass check valves.

I was unable to find a good rebuild kit a few years ago when I wanted one. Just bought a new master. All that I found had bad seals from sitting on the shelf for years.

But now this is my goto for seals and packing... https://www.zatkoff.com/catalog/master-catalog/molded-packings-piston-seals

Alan Brase Thu Jan 14, 2021 11:44 pm

Well, now it comes up, I don't see any listed either in regular aftermarket sources.
I, too will need to find a 1967 master cylinder kit.

Peter - Belgium Fri Jan 15, 2021 12:56 am

Exactly... also never found a source for a rebuild kit, only complete master cilinders which are very expensive.

That is why most (including me sofar on all previous builts) always convert to the baywindow servo master to get to a dual circuit. Now I had an OG 67 master wanted to give that a try, but seems will need to convert again!

thanks!

Tizian Fri Jan 15, 2021 1:46 am

Hi Peter,

I would suggest to buy a new MC. Itís youíre life insurance ;-) and is still available from ATE. Just google it:

ATE 03.2122-0704.3

Itís not too expensive in my opinion...

flemcadiddlehopper Sun Jan 17, 2021 6:26 pm

To answer your first question in the original post. The piston at rest should be just ahead of the fluid reservoir. The moment the piston begins to move it passes the hole there by pushing all fluid out the brake line port. When the piston returns it opens the reservoir port to allow fluid to flow in.
This is why pedal free play adjustment is so crucial. If the piston does not return and open that reservoir port, every application of the pedal will build up fluid pressure in that brake line until, it locks the brakes on.

And, just buy a new master cylinder....be able to stop is kinda important. It may be expensive, but it's cheaper than your bus and easier on you sole than killing a bus full of nuns and orphans.

Gordo.



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