High pitch noise engine area at 2500to 3200 rpm under light load

If the squealing is coming from under the hood while the engine in running then it could be a number of things such as an idler bearing, water pump bearing, or possibly an air conditioner or alternator bearing. Other possibilities are belts that are worn or have gotten wed from a bad water pump or have loosened up because of a bad belt tensioner. Take a long bar and touch each area that seems to be making the noise. If you can feel the vibration or hear the squeal when you touch the area, then you found your noise.

Sounds like water pump! If it was last changed 60k when timing belt done could need doing! If not timing belt tensioner! When timing belt is done it is good practice to replace water pump and belt tensioners at the same time!

Have you checked the tension on the alternator or any other belt drive in the engine bay?

The lost acceleration is of major concern. Maybe you have lost your water pump. It would work great for a few miles when you start out and then gradually heat up and loose performance. The fluid would eventually boil over? Maybe a bearing on the camshaft is expressing it's discontent and causing extra load for the engine to overcome. Try to determine where the noise is coming from.
The serpentine belt connects the alternator, water pump, power steering, front timing pulley, fan, and front timing pulley. All these components generate a parasitic load on your engine. If the engine has to work harder because of increased load it could be any of these components. I'd definitely check the water pump listening for noise while running. Look for obvious things related to the belt and its' components.
Check the serpentine belt for wear. May indicate pulley misalignment or wear. There exists two idler pulleys that have small bearings that wear out and squealing noises. Check those for wobble with the tension off the belt. They are pretty cheap so replace them if any concern at all.
Power steering pumps cavitate and make a high pitch gear whining sound if fluids are low or gears warn of. Check the fluid and top off to the correct level.
Best wishes,
TF

When the AC compressor kicks on, an electrical load is placed on the alternator and the drive belt that turns the alternator pulley, if not tight enough, can cause the belt to squeal. Replacing the belt should help with that noise if the belt is stretched from wear. The screeching noise can be from a bad idler pulley, a bad belt tensioner pulley or a bad alternator pulley or a failing clutch on a very old ac compressor and rarely a water pump pulley. To check pulleys remove the drive belt and turn them individually to see if they can be tilted up down or sideways with play in the "bearing" of the pulley. Also, you may wish to visually inspect the clutch on the ac and look for melted black rubber around the bolts that secure the clutch to the compressor (stinks,smokes and melts these rubber areas if ac compressor clutch fails).

sounds like the tensioner /or the water pump which acam also make the same kind of noise

Hi,
My first thought would be that a bearing on a rotating element is going out. Since you stated you checked the alternator and replaced the tensioner, I would next, focus on possibility of water pump, power steering pump or A/C compressor. Maybe you can isolate the sound to determine which.
I would even go so far as to dowse them with WD40 at the pulley bearing locations, one at a time.
Hope this helps... Good luck!

Could be several things. WHICH ENGINE?.. 4 cylinder (has three belts, power steering/water pump, alternator & A/C compressor, one tensioner pully A/C compressor), The V6 2.7 (has only one belt, 1 Idler pully and 1 tensioner pully), the V6 3.5 has two belts - A/C/alternator, and power steering - there are two tensioner pullys). Noises can be caused by the belt(s) themselves, pullys, bearings, pully bearings, water pump shaft bearings (or belts/pullys rubbing up against something). Let's not forget that there is also belt(s) behind the Timing Belt cover as well as pullys and bearings associated with the timing system. You could start by removing one accy drive belt at a time (alternator, water pump, compressor, power steering, etc) to see whether or not the noise goes away in each case. If after each case, you discover the noise is still there, it's probably behind the timing belt cover (idler/tensioner pully, water pump shaft bearing, crankshaft bearing, etc.). Good Luck

The trick is to take off the belt and spin the different things and see if any of them make the noise you hear.
Water pump, alternator, power steering, air pump, belt tensioner pulley. You could also briefly (30 seconds) run the engine without the belt and see if it still makes the noise.

For prices, you can check autozone.com or partsamerica.com

I have a 1995 xj6....same problem. I replaced the belts, water pump, and the alternator. Still does it. As I play with the tension on the belt (belt that drives water pump, alternator) it goes away and comes back. If I remove the belt, the metal to metal screech stops. I then, with just the belt, turned the main pulley on the front of the engine, and there was the sound! The main pulley has 2 belts that run on it. Also, 2 pulley tracks. They SHOULD move simultaneously and be super meshed. But the rear one moves on its own under tension until it warms up and I guess, the bushing maybe expands. Now.....how do I fix it??????