For what it's worth, I've had a few ML's that don't seem to bleed the air thoroughly after parts replacement. For instance, after replacing a NOISY P/S pump and driving around for a while, there was still some minor groaning heard when turning the wheel. I thought the new pump was NFG so I went to the parts counter to get another one. We didn't have one in stock, so I ordered one for the following day. The next day I started it up and the noise was gone!!! Sitting overnight must've allowed the trapped air to rise to the top of the reservoir.