[v8volvo]

If the fluid was "bubbling," that is a sign that it was aerated because the reservoir level got too low and allowed the pump to suck in air. The aerated fluid causes pump cavitation, which you can hear as the groaning noise when you turn the wheel.

Don't despair about your rack yet. Discolored and low fluid can be caused by a number of things, either the rack, or the pump, or having someone add the wrong fluid, etc.

Where exactly is the leak coming from? Could be from the rack, but also from the PS pump itself, one of the pressure or return hoses or fittings, etc. If you have been driving with torn steering rack boots for some time, that can allow grit in that tears up the rack seals and causes leakage, but assuming you have not done that, the leak is just as likely to be something much more minor, especially if it started suddenly.

Volvo power steering systems should use only clean Type F automatic transmission fluid, none of the generic "power steering fluid" you might find at your local parts store. Once you find and fix the leak, you should give the system a full flush to get rid of the old discolored fluid and ensure the right stuff is in there.

Don't drive it with the pump making that noise, or you will quickly find that your need a new PS pump as well as fixing whatever the leak is. If you need to drive it, then remove the belt from the PS pump first, or top the system up with new ATF and run the wheel back and forth until you are sure the level is high enough and there are no more air bubbles showing up in the fluid or moaning noises coming from the pump.

George