Rattling sound coming from engine bay.
 

It's like a high pitch ping/rattle type sound that is loudest when I first start up the engine (when cold) and generally goes away when I push the engine hard. It has slowly been getting louder. It doesnt vary with speed or with engine RPM, though it is definitely more common when the engine is idling (maybe just more noticeable)

For the life of me I cannot figure out what is making the noise. It appears to be coming from the front of the engine somewhere but I can find nothing that is loose. Anyone have any ideas?

I had a rattling sound from the front of my engine over Thanksgiving break. Turned out to be 2 of the 4 bolts in the crank pulley had sheared off.

Hmm that would suck. Im going to jack the car up tomorrow and run with the garage door open to see where the sound is coming from.

Hmm , I thought it was my radiator fan but I finally tracked it down to a loose bolt next to the crank. Some random metal bit was hitting the crack pulley, bouncing off, hitting the crank pulley, bouncing off... Ping ping ping ping pipipiing ping. Annoying but it is finally gone and motor only makes exhaust noises again.

Ok now I need help tightening the fan blade bolt on the radiator fan. It is loose now and there is nothing to torque against as the bolt is attached to the stator and it turns whenever I try to tighten it.

Arg.