The power steering pumps are the most common cause, not from the pulley, but from the buzzing of the internal check valve. We have already had instances where rebuilt pumps are just as noisy at first but the buzzing dies down over time. You can verify that by listening with a stethoscope at the connection for the high pressure line where it leaves the pump. This is common enough that we don't even bother to diagnose the generators or water pumps. A quick poke with the stethoscope is all it takes.
That buzzing noise is a lot different than the squeak or chirp from the serpentine belt. Don't use any type of lubricants or anti-squeal sprays on those belts as road debris and dust will stick to it and make the squealing worse. To identify a belt squeal, dribble a little water on the smooth side of the belt while the engine is running and the noise is present. If the noise changes, suspect one of the pulleys is misaligned. If nothing was recently replaced, that means the spring-loaded tensioner pulley is the most common cause. The pivot wears and lets the entire arm sit crooked, then the belt has to slide sideways across it as it goes around it. That sets up the squeal.
If the noise was not there until after something was replaced, check that item to be sure it's mounted correctly. The belt should be perfectly inline along all of the pulleys. Look for one where the belt is off-center compared to the rest of them, typically by 1/8" or more.
Monday, May 1st, 2017 AT 8:34 PM