I finally had some time to do the full rebuild on the steering gear box (1997 D1). Now that I have it completely apart the reason for the leaking rebuilt units becomes obvious. Looking at the kits for the D1 (including the one I bought from an LR parts seller on ebay) most are missing the single most important parts: valve seals.
The D1 workshop manual outlines the procedure for installing new valve seals. It requires a special mandrel and warming up the teflon seals to install them. These seals are missing from the kits. The mandrel I can spin up on a lathe with little effort.
The valve is a torque actuated flow divider. If the seals on the valve are worn or the valve bore is worn the high pressure fluid bypasses the valve by leaking into the box cavity. The pressure is much more than any of the seals are designed to hold so it leaks, leaks, leaks. A "rebuild" with one of the D1 kits will hold for a while but is dependent on the condition of the valve. I have not yet disassembled the valve to look at it's interior condition. That too could be a contributor. The last potential culprit is the relief valve but less likely unless there is contamination or damage.
There are some D1 kits that appear to have the valve seals at double or triple the price of the STC2847 based kits. I have found one kit from a seller in Oz that has the valve seals.
So now here I sit with my steering in pieces and missing parts. :banghead: Being in rural AZ there is a good chance I can't get a COMPLETE kit here in any reasonable time frame. :ack:
The lesson: Don't waste your time and money with the STC2847 based kits if you have a leaking, higher mileage steering box and want to do the rebuild yourself. Make sure you get a kit with the three teflon valve seals included. Without these the bypassed fluid will cause the box to leak.
The rebuild is simple and easy to do IF THE KIT HAS ALL THE PARTS.
Do any of our lurking vendors have the teflon valve seals?