the pump on the xantia not only controls the steering it controls the brakes & suspention as well so does a lot of work, first check the drive belt is tight & replace if it looks at all suspect, have the filters in the L H M reservoir been cleaned ?they need doing at the recommended service intervals, and replace the fluid at the same time the if non of these are the problem possible pump, steering pinion, or flow distributor fault, invest in an haynes manual a mine of information for these systems
bob k, May 2009