Stiff steering

[Reiny]

the power steering on my 300tdi 90 has suddenly become very stiff when the vehicle is stationery. I was trying to park while holding the wheel on full lock when I felt a "kick" through the steering wheel. This happened last Saturday. Since then, I have observed that the problem gets worse at times and better at others; i.e. at times the wheel is only slightly stiff but on other occasions, I need to use both hands to turn the wheel). If the vehicle is rolling, even if it's barely moving, the steering feels totally normal. This problem manifested itself on two other occasions three months ago but the situation returned to normal within a day. Yesterday I gave the steering column UJ's a thorough bathing in WD40 but felt very little difference. The pump was replaced with a genuine ZF item almost 3 years ago and there are no leaks from the pump or box. The only leaks I have are from the reservoir pipes. What could the cause be?

[pinny]

the power steering on my 300tdi 90 has suddenly become very stiff when the vehicle is stationery. I was trying to park while holding the wheel on full lock when I felt a "kick" through the steering wheel. This happened last Saturday. Since then, I have observed that the problem gets worse at times and better at others; i.e. at times the wheel is only slightly stiff but on other occasions, I need to use both hands to turn the wheel). If the vehicle is rolling, even if it's barely moving, the steering feels totally normal. This problem manifested itself on two other occasions three months ago but the situation returned to normal within a day. Yesterday I gave the steering column UJ's a thorough bathing in WD40 but felt very little difference. The pump was replaced with a genuine ZF item almost 3 years ago and there are no leaks from the pump or box. The only leaks I have are from the reservoir pipes. What could the cause be?

if the belt slipping on the pulley i had a similar problem replaced the belt and its is ok now