This just started today. After my 300d was started the second time today I heard what I can only discribe as a low pitch whine or roar from the engine bay. After about 10 seconds it went away. Has happened on and off all day only on startup and I can't place this sound even with the hood up and looking for the source. I want to say bad bearing in the water pump? I don't know any other way to describe this, car is running just fine, not hot, no loss of coolent or any other fluids. Just the noise and it sounds pretty bad. Any ideas or questions that may bring about an answer?