Though i don't understand the reason why,my pas box popped the seal and started leaking when i turned the wheel without the pump running.It then settled down and stopped leaking for a few months but eventually started leaking again.I bought a seal kit from my local independant man (the landy is a 1990TD with a 6 bolt box on).The main seal to change is the shaft seal on the shaft for the drop arm ,i changed some others as well but not all as its like a Swiss watch inside these things.That was about 18 months ago and touch wood it has been ok since,i did'nt have a manual so just muddled my way through,the hardest bit was getting the bl***y drop arm off.
Cheers,Mick.