http://www.youtube.com/watch?v=ATjdVu1Ff-Q

if it does that ^^^^ then the rack is fucked. its either a tooth or a seal.

mine does it but no way near as bad. had it when i bought the car 2 years ago and ford diagnosed the seal on mine (something to do with changing the steering direction and the pressurised fluid swapping sides) and replaced the fluid which helped and is the only reason why its lasted any longer but does need swaping asap. incidently i think i have a little play in one of the track rods too.

hope that helps you mate, i know you've had the odd issue with your car which is a shame as they're good motors.

what colour is your pas fluid? if its grey then thats probably why its gone. i think if it was regularly changed then this wouldn't be such a common fault.