2007 xc90 2.5t stiff steering at standing

[jonny2]

i have had stiff steering at parking for along time now.this is only felt at standing and trying to park. it gets to the point that i cant turn the steering weel at all. this problem comes and goes ,once everything is fine and aday later it reapears. the power pump and steering box have been remooved disasembeld and look fine.the two solenoids have been changed too but that too hasent helped.
can you please help.