Over the last few years, every winter in cold weather I'll start the vehicle and hear the treaded power steering motor making a noise that sounds like ZZZZZZZZZZ. This happens for the first 10 minutes of driving. You can hear the sound while driving forwards when the wheel is perfectly straight. You don't have to be turning the wheel.

The power steering system has never leaked. The fluid is at the full mark.

I've replaced the power steering reservoir unit last year.

Each year I use a full can of CHF 11s to drain, fill, drain, fill method in an attempt to keep the fluid clean.

I replace the serpentine belt each year and clean the pulleys during the process to check for potential oils on the belt or pulleys.

This winter I heard the ZZZZZZZ sound again and started the annual process to drain and fill, drain and fill using another can of CHF.

It looks like I might have solved the issue after numerous cans, but was this just a band aid? I can't help but think there is an O ring somewhere that is letting cold air into the system.

Maybe the issue is the power steering torque converter servotronic unit connected to the rack?