I have been trying to track down a strange noise that I encounter on my 93 190E 2.3. It only occurs when the car is at idle and is in gear (with brake depressed). It is almost a rattle (has that bouncy,spring rattle that you hear from a rod almost), it is worst when the car is cold and is placed in REVERSE (automatic). I used a wooden handle to listen to the top and bottom end and eliminated the engine itself (and there are no problems with driving or acceleration - engine is wonderfully smooth and powerful). While checking all of the accessories out on the engine, I found a disturbing amount of endplay in the PS pump (both wobble and in-and-out motion). Could a worn power steering pump possibly cause this noise?