All of a sudden I started hearing strange noise at the top of the engine (camry 2006 2.4l), the noise seems to be around the alternator and the exhaust manifold and when I rev the engine I don't seem to hear any noise. So, I remove the drive belt and start the engine, I couldn't hear any noise (the engine sound so cool). Immediately I install the belt back the noise came back. I need assistance on what could be wrong.

 

Get a section of rubber hose to use as a stethoscope to narrow down the area of the noise.
Then with belt off rotate each pulley powered by that belt and feel for binding, looseness and listen for noise. Could be an idler pulley, water pump, alternator bearing.

Also listen to the area under the front timing chain area for noise and the upper part of the timing cover where the VVTi pulley is.

 

Can you post a video of the noise.