I have a 2001 300M which suddenly started making a top engine noise. My mechanic thought that it may be some carbon that came loose and was rattling around under the valve cover so he ran some detergent through the engine and although it got better it's still there.

When the engine is cold, you don't hear it but once it gets warm you can here it when you're driving down the street with the windows up and the A/C on. To my mechanic, it sounds like a double tick (not a lifter)...to me it sounds like 2 single ticks.

The car has 120K on her and has the oil changed religiously at 3,000 miles since new with good quality oil (typically Quaker State or Valvoline)

Any thoughts?

Jim