I have an 04 f150 lariat 4x4 and for the past 3 weeks my belt has been squeaking bad. I've listened to it and it is definitely coming from the power steering pulley. I was wanting to know if it was my belt, power steering pump, or the tensioner.

 

How old is the belt? if it's original and/or over 3 years old, change it. If it has cracks in the grooved side, change it.

The squeal is most likely a pulley though. An easy temporary test is to rub a bar of soap on the inner side of the belt; if the squeal stops, it's the belt.

If the belt is old and/or cracked, it needs replacement anyhow, even if it does not squeak. Some parts stores will give you a simple plastic tool (looks like an opened paper clip) to test the depth of the grooves; if they are "rounded" or shallow, it needs replacement.

 

take the belt off an hand-spin your tensioner pulley... if you can here any squeaking noise than that would be your problem... easy fix - $30 part from autozone and three bolts to remove

 

You're refering to the tensioner pulley....good point to make for testing. With the belt removed, you could also hand spin the other accessory pulleys perhaps to see if their bearings squeal as well.