407 Steering issues

[red080]

I have a Peugeot 407 with this issue steering jerk from left to right

I changed the steering rack which has a small leak and when I installed the other one, worked a bit good and start jerk from left to right.I tought the rack was damaged and installed back the old one,but still doing the same,which was working well before I took it off.I can't understand what is wrong.The angle sensor?

[Stickyfinger]

Have you put the pipes on back to front ?

[GiveMeABreak]

...or multiple air locks in the system?