- If you really want to be thorough have someone run the engine with the front wheels of the ground and while turning the steering left to right (full lock) keep pouring fluid into the reservoir to flush out all the fluid in the pipes. I didn't bother with this as I was on my own.
I was also on my own. I jacked up the right-front wheel and removed the wheel arch liner to get access from below. Then I disconnected the return hose and directed it into a bucket - and then, I started the engine.
You wouldn't believe the rate at which the fluid pumps out - emptied the reservoir in about a second and the pump started gurgling/spitting an emulsified air/fluid mix everywhere. I was meanwhile attempting to pour in the new fluid, which was some special clear type incorporating a seal conditioner (not that I was having any problems, but thought it would be preventative maintenance). I thought it would gently flush out the old fluid, but it was all over (the suspension, the brake, the driveway...) in about a second.
I went back to the shop for another litre (this time of fluid not including a seal conditioner) - knowing that all the dirty fluid had been pumped out, I reconnected the return pipe, filled up the reservoir, and turned the steering from lock to lock several times while pondering whether I should have done this in the second or two as the old fluid was being pumped out
If the system has emptied itself, it takes some time to get all the air out, and you can expect a great deal of whining and bubbles until this happens. It eventually self-bleeds but obviously needs several top-ups to do so.
So, the advice to drain the fluid without the engine running is probably good - changing most of the fishy-smelling will suffice - and my advice is that if you do try to flush it, have at least two litres of new fluid on hand and expect to make a mess
The fact that the noise goes away is a good sign and I think the level is just a bit low - allowing air to get in during startup and the air slowly works its way out.
I suspect that ongoing moaning/whining means one of three things:
- old worn-out fluid foaming/pump cavitation - hence the need to change the fluid
- air getting into the fluid - loose hose connection allowing air in but not fluid out?
- pump worn out (perhaps due to not having fluid changed)
I know for a fact that there have been cases where power steering pumps have worn out and needed replacing to fix the noise. Alfa 156 was where I saw that, but Alfa 159 has a similar problem due to a faulty reservoir screen mesh restricting the flow of fluid. For my Gtv, at least I verified that there was NO restriction to the flow