After numerous forum searches, I can’t seem to find a definitive answer to the question – does the ML320 power steering reservoir have an internal filter or screen in the reservoir?

I recently replaced the failing o-ring between the reservoir and the power steering pump and can NOT get the wining noise to disappear. I’ve gone through several different air bleeding routines to insure there is no air in the PS system. I’ve jacked the front end of the SUV and moved the steering wheel from lock to lock at least 50 times over several days with the car started and stopped both. I’ve added the MB additive to reservoir. I insured there is the correct level of fluid and there are no visible leaks.

The most significant noise occurs when the engine is 1200+rpms while turning. There is hardly a noteworthy noise while turning or steering if the engine remains at a low rpm. The noise seems to have taken on a slight buzzing noise in addition to the whining while turning.

The ML320 has 120,000ish miles, so could a clogged screen or filter internal to the reservoir be causing my dilemma? Or should I begin searching for a replacement PS pump?

Thanks in advance for any thoughts on this matter.

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Russell McMahon
Tulsa, OK
2001 CLK 320
1992 400se
1993 400e
2000 320ML