There were several different fits. Some used independent lines from the PWDA valve to the front corners, while others used a single line to the front cross member and a T-piece to each corner. I can’t see either having much mechanical advantage, but the T-piece system may be easier to fit for many people and uses less pipe. the cost of the pipe is probably similar to the cost of the T-piece and the extra couple of unions to fit it, so I doubt it was done for economics. regardless, either system should be fine.

109s twin leading shoe front brakes are very tricky to bleed. The only way of getting all of the air out is to remove the hubs and the brake backplate, lay the backplate horizontal so that the pipes are on top and the cylinders and shoes underneath, clamp the pistons fully retracted (shoes removed) or tie the shoes back with the adjusters backed off and then bleed – this technique puts the outlet ports of the cylinders at the top, so any air will be forced out. It’s time consuming but worthwhile, and it gives you an opportunity to inspect and service the wheel bearings and hub seal. A bit of a bodge way of doing the same thing is to remove the shoes and pistons and lay a piece of medium gauge fishing line into the bores, and making sure the line stays at the 12o’clock position of each bore, refit the pistons. The fishing line will break the seal, allowing the air to be expelled while you gently bleed the system. A each bore becomes filled with the fluid, the fluid will start to leak out the top of each piston. At this point, gently and smoothly remove the fishing line. The fishing line is soft and smooth enough to avoid damaging the seals. Don’t try this with wire, thread or other substitutes.

Failing all of that, suspect the master cylinder; it may have been to worn for overhaul or the new seals may be of poor quality or damaged, especially since the overhaul kits are almost invariably after-market rather than genuine parts.

I hope you get to the bottom of it.

If you have a single line brake system on your SIII, you could just fit a remote servo rather than the Land Rover unit; the former would be available from a motorsport or kit car parts supplier and just fits in-line to the exisiting master cylinder’s output line before it splits to the axles, while the latter wlll require a new pedal box and compatible master cylinder. If I’m not mistaken, those master cylinders specified for SIIIs with servos were for dual line systems with 11″ brakes and twin leading shoe systems. I suspect that you could probably use a dual circuit master cylinder and split the single line system to become dual line without replacing all the axle brake components – the master cylinder produces equal pressure in each of the dual lines, so you wouldn’t have to worry about brake balancing.

The servo won’t increase braking efficiency or power if you retain the existing brake system, but the brakes will require much less pedal force. If you think you need more powerfull braking, then a more affordable way than fitting one of the disc brake conversions is to fit the entire system from a 109 or post 1980 88 with the dual line, 11″ system.