CB Master Cylinder Debacle

[mawalker]

Hello all, I’m desperately in need of advice relating to the install of a CB master cylinder for my 88” 2A. I’m working to complete a brake system overhaul in which almost all of the brake-related items have been replaced.

I’m having a nightmare of a time with the new CB master cylinders I’ve purchased from RN leaking straight away. I don’t in anyway mean to bash RN (they’ve been more than helpful with customer service) but I am at my wit’s end here. I’ve just installed the 3rd new master from RN today and again it’s leaking!!

I’ve gotten the master installed in the tower, tower to bulkhead, installed lines, and filled reservoir with fluid. I’m using a Gunson eezibleed tool at 10-14 psi to pressure bleed the system. With the most recent master I’ve installed there was a noticeable amount of fluid leaking from the bottom of the pushrod boot once pressure was applied and it started running down the brake pedal. Seems to be leaking even without pressure applied. I’ve been careful to only use new LMA brake fluid and have barely worked the pedal (only slightly to fit through the bulkhead for reinstall).

This is getting incredibly old and frustrating, and I’m not sure what my options are here. My original master is not rebuildable, and the others I’ve seen offered are either Britpart or Allmakes (which appears to be what RN is selling). Genuine are like hen’s teeth and the few I’ve found are $$$ and I wonder if the seals are even usable in them.

I had thought I had just gotten a bad master (okay, it can happen) but after this third one I’m either doing something incredibly wrong (what???) or RN got a bad batch of these and all the ones I’ve gotten have the same issue.

Has anyone else had similar problems or have any thoughts on how I should proceed. Many thanks!

[jp-]

The CB master cylinders are notoriously difficult to bleed and otherwise troublesome (a bad batch is certainly possible also). I gave up on them a long, long time ago. The best thing to do is go to a dual power brake master and booster (this necessitates running separate front and rear brake lines, different pedal tower, etc.). If that's not in the cards right now, and you want to retain the single line system, I would at least switch to the CV style master cylinder. I ran this style for years on my 109 SW and 88 SW.

As always, be careful when working on/testing your brakes.

Note, if you plan on updating the front brakes at some point to discs, then a dual power and booster setup is what you'll need anyway.
Info on the dual power upgrade here: http://www.expeditionlandrover.info/dual_brake_conv.htm

[mawalker]

Thanks for your valuable advice. It seems from my research also that the CV master cylinder may be the way to go. From my research it looks that the only change which may be required to fit the CV style master is the inlet/outlet brake line orientation. Are you aware of any other modifications which may be required?

[jp-]

I think that's it. There may be an adapter required on the inlet or outlet, but I can't remember.