My 2010 4.4 has a power steering problem. Most of the time it works fine, but sometimes when manoeuvring into a parking space the steering struggles to keep up. If I put the box into neutral & bring the revs up the steering frees up, but that obviously doesn't help with parking. A few months ago a corroded pipe was causing the PS fluid to leak & so was replaced, & it's since then the problem started. The garage has checked the system & can't fine anything, but unfortunately it doesn't seem to act up when they have it.
Any ideas as to what it could be?

If the steering goes heavy then it could be the Servotronic Valve Transducer, part number QFW500040 Did the garage read the codes?

The garage did read the the codes but nothing showed up, but they mentioned some kind of valve that opens when driving at slow speed. Is this what you are referring to? They suggested that if the problem persisted their auto electrical man could pop in & take a look.

That’s the one. Number 12K528 in the diagram.

Click image to enlarge

Thanks for your help with this. I'll give the garage a call in the morning.

If the problem always gets better when you increase engine speed its most likely to be a problem with the PAS pump.
The Pump can be checked for output by having the car in neutral with engine running at idle and adding a small amount of steering lock & lightly holding the steering wheel.
If you then increase the engine speed and feel the steering wheel trying to turn more it indicates the PAS pump output is increasing with engine speed - indicating the pump is worn / faulty.
If the wheel doesn't want to turn as the revs increase it indicates the PAS pump is already giving full output & is OK (The pump achieves maximum output at engine idle & then has a pressure valve to limit any extra output).

The Servotronic valve on the steering rack decreases assistance as vehicle speed increases and shouldn't be effected at all by engine speed.
You can overide its control by the BCM to add full assistance all the time for testing purposes by disconnecting its connector to the vehicle and supplying 12V direct to the valve. Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk