Having some bother bleeding power steering

Evenin all, I've been haveing an wee problem with trying to bleed the power steering on my 86 110 2.5D N/A, i.e. it wont....

Its a bit of a nightmare because the system is a bit pic n' mix as it wasnt fitted at the factory, the box is the later (metric) type with the square top and the pump is an early (impeial) cast casing type. I had to replace the HP pipe due to a leak and had to turn the pump round (HP on top, LP on bottom) to fit the new one and got a bit of hydraulic pipe to use as the LP line.

Since then it hasnt worked. Fluid comes out of the bleed nipple on the box when turning one way but then gets sucked back in when turning the other way? Is this normal? Also whats the proper procedure for bleeding the system? I might just be doing it wrong.

P.S. everything moves smooth with the front wheels in the air, no tight spots and what not.

Any advice would be great! Ta!

another pump perhaps return lp pipe can just be hose and doesnt want to be to small bore

Make sure everything is tight fill it up and turn lock to lock a few times and that should be it . If you have the bleed nipple open every time you turn the wheel you will be sucking air

Im starting to think it might be the pump as i have tried all the normal methods of bleeding and have even taken it for a short drive but still no improvement

Im guessing a loose belt wont help things? the adjustment is on the stops and the belt is still a bit slack.