I have a slight knock in engine compartment. When the serpentine belt removed, no knock. Replaced idler pulley since when spun manually it seemed to be the worst (and cheapest) and knock still persist.... Approx 50k miles on car. I cannot tell if it is possibly the alternator (3 years old, cheapy from Carquest) or is it possible the crankshaft bearing? Perhaps it only makes the crankshaft bearing noise when the serpentine belt is on providing pressure/resistance? The noise is towards the front of the motor and does not appear to be from the power steering pump. Water pump is new.

Thoughts? Thank you in advance.

Would recommend using a mechanical stethoscope to help pinpoint/locate the offending accessory.

These engines are notorious for harmonic balancer failures that cause a knocking sound.

So this makes noise with or without the belt on?

With the engine off and belt off use a stethoscope or a long screwdriver with the handle shoved against your ear. Put the other end on each accessory and spin the pulley. Anything besides a smooth sound or barely a sound and you probably have found your culprit. If you're not quite familiar with how a quiet bearing sounds versus a noisy one, listen to all of them, especially your brand new idler pulley. Odds are really really slim that more than one accessory decided to eat a bearing.

Wow!

If it was a crank bearing it would do it with or without a belt.

Does the balancer remove the same as the idler pulley?

correct, no belt no noise. It seems to be the harmonic balancer... I have seen videos showing a breaker bar wedged against the frame of the car and then crank motor - i see nothing but catastrophic failure doing that... is there a sound, professional way?

Do you notice the balancer wobbling with the belt on? With the engine off, grab the outer ring of the balancer and see if there is any movement when you pull/push on it....

As for removal, if the face has 3 holes 120 degrees apart, you need a puller.....

Does it sound like this?:

If not, it would be good to capture the noise and share it with us to help track it down.

Dan has a good write up on scope of work required to remove the harmonic balancer.
https://www.gmforum.com/mechanical-1...cement-286278/