I have a 2012 GLK and a 2005 C240 4matic with 68000miles. I notice that the power steering pump has a "winey"
noise, however the fluid level is perfect and the car steers fine. Does anyone now if there has been recall on this or it is normal ?

MB suggest a "special" additive from a company Lubrizol.

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If the noise is on the C240 the noise may be coming from the A/C compressor pulley. Very common issue and easy to mistake for the P/S pump.