AOA pakwheelers. some days ago my steering got completely stiff.it was hard to turn it on idle whether if i raced the car it sometymes got normal.i changed the power pump.it was normal for some days,but after some days it got a little hard.yesterday i changed the suction valve of the pump so the steering was back to normal,but now the prob is that when i drive the car for long like when i cover 20kms etc after that the steering gets 20% harder.and when i switch off the car and after some tyme when its temp is cold then its normal for some tyme until i drive for continous 20-30kms. i mean to say it was not completely soft like a power steering,just 20% harder.now the prob is even if i hold the car raced, even then the steering is 20% harder. what might be the reason?thanx