Td5 power steering noises

On my 90 td5 When I turn left at low speed or stationary there is a irritating whining noise from I suspect the power steering pump?but nothing when I turn it right.
Then when on the move a steady left hander creates an er er er er noise and vibration through the steering wheel again nothing when turning right
Almost like the tyre is fouling summart but it isn't.
I swapped front for back tyres and it's still doing it.
The whining has happened since I got the car but the cornering noise has not long started.
Are these symptoms for a knackered power steering pump?
Is there anything I can try before I replace the pump?
I'm not aware of a filter in the fluid, is there one?
I stumped with this one surly a buggered pump should whine all the time?
Please help, cheers Dave

try it with drag link disconnected

Is that to eliminate one side?

No that's the track rod, I'm lost what does that tell me?

it eliminates everything apart from pump and box

Could be a wheel bearing causing the grief. A mate of mine had almost identical problem with his disco. As jamesmartin says disconnecting drag link will go a long way towards identifying the source of the problem as additinal load on the steering from any source will cause it to groan and moan.

Sound then I will do it, cheers