brake master cylinder

hello again, having looked at the master cylinder it requires replaceing: it is a 1981 mini pickup with drums all round, with a BLACK plastic identification band
on it (type 2 tandem)
The only replacement is the type 3 tandem with the yellow ID tag. Haynes manual states that thie type 3 (1985 on) has a stepped bore and primary and secondary circuits have been reversed.
Does this mean if i retro fit a type 3 i have to put the top brake line to the bottom hole and the bottom to the top ?
if not please explain A) how to tell the primary and secondary circuits from looking at the master cylinder and B) which is primary - front or rear brakes?
I need to work on this quick as i wanted it MoT'd by end of month - all that is left is the excessive brake pedal movement - ie nearly to the floor. I realise it has no servo and the brakes are adjusted and good shoes etc.
any help most appreciated.
RS
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I just had the same problem, yes put the original top pipe in the bottom hole and the original bottom pipe in the top hole, BLEED thoroughly. there is a leaflet in the new master cylinder box that explains all this

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I'm having exactly the same problem - but I have stripped mine right down to the shell - so I've nothing to 'swap'. I'm having to start from scratch.
So.
I think I have discovered that using the yellow tagged stepped bore M/C...
the top outlets (10mm) goes to the fronts and this is called the secondary circuit.
The bottom outlet (12mm) goes to the rears, and is called the primary circuit.
If all the info I have collected is correct.
Can anyone confirm this please before I do the plumbing.
Thanks
Peter
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dont both pipes go to the compensator on the left side

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"jacko" wrote in message

they do, the compensator valve splits the braking force 75% front 25% to stop the rears from locking up. ie you have to plumb it in correctly. you do not want 75% braking at the rear... or do i....? would be interesting on wet/ icy roads....
RS
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Thanks for the tips Jacko and RS.
I have been reading Keith Calver's advice on front / rear split braking systems, and the problems some have with the pressure regulator valve (FM7821)
www.minimania.com/web/SCatagory/BRAKES/DisplayType/Calver%27s%20Corner/DisplayID/942/ArticleV.cfm
Hope the link works...
He recommends scrapping this unit and instead either fitting an MS72 adjustable regulator / bias valve if you can get hold of one (which I couldn't) or modifying a rear brake proportioning valve (the one that sits on the rear subframe) to make it adjustable.
He suggests fitting the adjustable unit on the rear circuit under the bonnet fixed somehwre convenient on the bulkhead with a tee on the rear subby and this is what I plan to do.
As I said, I think I have identified that on the yellow banded M/C, the top (smaller 10mm) outlet feeds the fronts and the bottom (larger 12mm) outlet feeds the rears.
One or two on this NG have talked about this modification in the past.
If I have this wrong or if anyone has done this mod sucessfully I would be grateful for your views.
Best wishes.
Peter
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I think the MS72 is out of production but there is one in the catalogue below described as a "brake proportioning valve" looking closely it appears to be made by Ford Racing. .
http://www.nfauto.co.uk/download/cataloguejuly2005.pdf
This shows you how to make one if you have one of the proportioning valves fitted under the rear subframe.
http://hometown.aol.com/dvandrews/bpvalve.htm
Cheers
Peter

www.minimania.com/web/SCatagory/BRAKES/DisplayType/Calver%27s%20Corner/Displ ayID/942/ArticleV.cfm
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