Hissing at the end stops is normal you are effectively closing a running tap that has 135 bar behind it so to protect the pump it vents over a relief valve and that is the noise you hear.
There is no diagnostics for the pump other than is it working and sounds ok for us, and for the dealer they have a gauge that they can fit inline to test the max pressure of the pump.
Ian mentioned about their failures but I haven't heard of any on this forum or others.
Power steering hoses fail and I have seen plenty on the forums and experienced it for myself, not a horrific job on rhd cars.
Best thing is go drive one or two more like mentioned then you can compare
__________________
Del
|