I have an 02 F150 XLT 4.6L V8, my stepdad and I have replaced spark plugs, idler pulley, tensioner pulley, alternator, AC bearing, water pump and power steering pump but there’s still a metal on metal squealing/screeching coming from the engine compartment but only while the engine is under a load. Belt off, no noise, belt on screeching/squealing. We’re thinking it’s the harmonic balancer but after watching it while running g and tapping with a mallet it doesn’t move and makes no noise while turning by hand.
This is driving us nuts at this point, any suggestions would help.
Thanks folks.

 

Okay I see you replace the water pump

 

Turn the pulleys by hand with the belt off. You might find something.

 

Can you post up a video of the engine idling vs loaded and setting off the sound you are describing?

You don't mention if you replaced the belt. A stretched belt will causing screeching noises under load. There is also the fan clutch? If you didn't replace the FC, then remove it and try it and see if the noise goes away.

The only other thing I can think of is that one of the timing chain guides is damaged or in that area of the system. Not many more moving parts in that area, other than the oil pump.

Maybe if you post the video, maybe we can help you narrow it down better.

 

You also didn't mention the tensioner itself (just the pulley)....which should be replaced with the belt when the time comes. That's actually recommended by belt suppliers.

 

You would think if it makes the noise only when the belt is on and not when the belt is off that it would be the belt itself or something that is turned by the belt.

 

Here’s a video with the load, there’s no noise when the belt is off. Also some photos of the harmonic balancer.

https://youtube.com/shorts/i-zKLVLb0OI?feature=share

https://ibb.co/MRmCW01
https://ibb.co/1KC7kw0

 

All I hear on the video is a rattling noise, kind of like holding a stick against a high speed fan blade. Seems like you should feel it by rotating by hand all of the parts that get rotated by the belt. Could be alternator brushes or dry ball bearings. It's not a subtle noise, whatever is causing it should be felt by hand with the belt off. All of the rotating parts should rotate smoothly.

Here's another attempt to share the link. Not sure why yours seems off.

 

I'm think maybe your timing chain is riding against the case cover inside. The guide there may be broken and causing this sound.

I can't think of anything else in that area to make that particular noise except the tensioner. Put a screwdriver or something against the case and listen. Also listen to the belt tensioner you put on a new bearing, but not the tensioner arm. It could be the tensioner as Brew said.

Can you video it without the belt on also.

 

Any difference with ac on/off