Recently bought a 2009 MCS with 145k kilometres (90k miles) from the auctions. It has a noticeable whine from the engine especially when cold - noise reduces when warm. Diagnoses so far include isolating the water pump friction wheel drive to rule out the pump and removing the serpentine belt to rule out the ac unit, alternator and tensioner pulley. Whine still persists! Mechanics stethoscope indicates the whine is coming from inside the sump? Timing chain was on the way out so I replaced it. What are the symptoms of the oil pump chain or oil pump going bad - anyone had a noticeable whirr/whine when the engine is revved? If not oil pump/chain what else could be causing the noise?