Steering groan in Defender at carpark speeds

That moan or groan is quite common and usually caused by some air in the system. They are not self bleeding, there is a nut and screw on top of the steering box (offset, not central) where you can bleed it.
Generally only when cold, consider it a feature not a fault!
sheff

This is a common problem as you have seen. Its caused by pump cavitation when cold in thick fluid.
The actual noise is the pipes vibrating in their mounts.
There are a couple of fixes
1 check the rubber mounts on the steel pipes which run below the radiator too see whether there is any metal to metal contact. If so rectify.
2 fill with synthetic ATF, as its thinner when cold. I usually pull all the fluid from the reservoir with a syringe and refill and run and do again.. BUT if you are not afraid of a mess there's a bleed nipple on the box.
3 put up the front tyre pressures. More problem with wide tyres.
4 turn it a bit more slowly when cold.
regards Philip A

I have what sounds like the same symptoms on my 2000 Disco TD5. After raising the issue with a few LR mechanics, ie ULR and Range-Rov in Melbourne, they said 'thats normal'.
Although the noise does sound a bit worrying, I haven't really been too bothered about it if they reckon it is 'normal!'
Cheers

<div class='quotetop'>QUOTE</div><div class='quotemain'>2 fill with synthetic ATF, as its thinner when cold. I usually pull all the fluid from the reservoir with a syringe and refill and run and do again.[/b][/quote]

that's why I asked what fluid people were running. The OE fluid from about '98 has been Caltex PAS 14315/ Cold Climate P/S fluid. It has a much higher viscosity index and consequently a lower viscosity when cold than any mineral ATF I've seen specs on, as well as an additive to stop the moans. It really is good stuff. I'd be refilling with that if you didn't already have it in then see how it went.
FWIW, I'm curently running Castrol Transmax Z, a full synth (PAO/ester)ATF purely for high temp use, but it isn't as good as the Caltex PAS (semi-synthetic) fluid at low ambients/cold system.