I would say that if it's a high pitched whine that varies with engine speed, it is most likely the alternator. A lower pitched "whine" or "growling" might be the serp. belt Idler Pulley. In my experience, I never saw or heard of the tensioner pulley bearing falling so most likely rule that out. A bad tensioner usually makes a "rattling" type sound and is accompanied with belt "squeal"

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4 SEASONS A/C IDLER PULLEY BOLT -- 0.475 in. ID x 0.660 in. OD; A high quality.

 

That is what you call piston crash and usually breaks the piston. Depending on how it breaks the engine may keep running and cause very high pressure in the crankcase and blowing puffs of smoke to come out the from the oil filler tube every time the bad piston fires. If the piston come apart then pieces can jam between the piston and the head, stopping the engine.
Piston slap, as Massey indicated, is caused by too much clearance between the piston and the cylinder wall. It can be annoying, but usually harmless as long as it goes away after the engine gets to operating temperature.

 

holy resurrected thread, batman.

well idk if you guys saw this, but a while back my water pump started leaking and stopped working. I replaced it, and after removing it I saw that the crank bearing on the back of the pump was failed. The ***** were out of place, and it felt gravelly when turning by hand. Do you think that could be the cause of the noise?

 

deff could be a possibility you have to change it anyways