Done all that I'm thinking if it's not leaking from the rotating shaft seal and the only place its leaking is from the gasket joint then I can get away with leaving the arm on. This appears to be the only visible leak I'm going to clean it all up Make a new gasket for the end cap then fill it with oil and see if it leaks from the rotating shaft seal.
I've cleaned it up and filled it with oil It's now sat on the bench so I can identify exactly where it's leaking from Does anybody have an exploded diagram of a late steering box?
There's not a lot to them, a man of your talents will have no problem taking it apart! If you really want it off I'm in Teesside and have a hydraulic puller, I bent much bigger pullers than yours then popped it straight off with the hydraulic one, maybe I was lucky but it came off with hydraulic on and clapping it with hammers (with a bang!)
Sit it at the angle it would be on the bus also turn it a few times to move the fluid around like it is steering
It's definitely fresh I think I may have sussed where it's seeping from I just need to give it a while longer to be sure
