power streering fault 90

Help,
my 200 tdi has a steering fault at idle the streering is jerking when turning it lock to lock , it failed its mot on this, i have fitted a new box and pump all new ball joints and a new damper, all proir to it failing, belt is tight ive bleed the system but its still doing it , when you turn it it moves then hits a point where it jerks , and the belt sqeals does go pass this point but does it again further on , any ideas??????????????????????

does it do it with weight off the front wheels?
ie when its jacked up.
try it with engine running, then engine off and tell us what happens.
does the pump "groan" at any time, at idle and/or with revs raised?

Sounds as though you still have an airlock in the system.