J.W. Kiser

Eplebnista

I would top it off and see what happens next. When you top it off, bleed the system by turning the wheels right and left to the limit of travel several times with the engine running. Foam indicates a low fluid level and air in the system.

auzivision

In my experience, growling comes from low on fluid.

Maybe the cold caused cavitation resulting in bubbles or air is leaking in somewhere south of reservoir.

Reservoir needs to be full of fluid, not foam. I'd refill it.

auzivision

Oh yea, FYI... don't use typical power steering fluid.

928's use Dextron ATF as in automatic transmission fluid.

hacker-pschorr

After replacing the resivior and associated lines, I had a hell of a time getting the noise to go away (using the proper fluid...) I tried the lucus power steering fluid sauce, no change. I went through a few cycles of clearing out the resivior / refilling with the proper fluid then tried the Royal Purple power steering sauce....and the noise went away.

However, one "gotcha" with power steering, one line is under a vacuum & can suck in air through an old hose causing such issues while never showing a leak. I've never had this happen with a 928, I've had two other non-Porsche's with such an issue. Replacing the suction side hose fixed the issue.

J.W. Kiser

So basically start the car, work the pump pretty good to get the lines full, let the foam dissipate in the reservoir, and then top it off. Do I fill it to the top?

Eplebnista

You should fill it close to the top, start the car and then work the steering wheel all the way to the one side and then the other to bleed out air and then check the fluid level. Repeat as needed until full.

Simon928

This might not be the cause of your problem, but a loose bolt on the PS pump can cause the growling noises that you describe as well.

jpitman2

Growling can come from cavitation caused by a blocked inlet to the pump - cant get fluid. Had this happen once when pipe collapsed.
jp 83 Euro S AT 57k