I am hearing a noise from under the hood of my '99 C230K. It is not there upon startup, but appears when the car warms up. It is a sort of ticking noise. Not a metallic type of noise, sort of muffled. Not too loud. Speeds up with engine speed. Present with the car in motion or not. The car burns 0 oil. Sounds like from the direction of the head/block. No loss of power. I am taking it in on Monday but would be interested in what it may be beforehad or what tests the dealer should run. Thanks!