96 Ford Explorer XLT 4WD
193,000 miles
4.0L

There is a grinding noise during idle that picks up frequency when I increase the RPM's.

In the past 2 years I have replaced the Alternator, Idler Pully, & the Water Pump. The grinding became noticable about 4 months ago

I am guessing my problem is on the accessory belt. If I eliminate the new parts, it leaves me with the power steering pump and air conditioner compressor.

What do you think? How might I figure out who is the culprit.

If you are pretty sure it's a belt driven item then check them again - even ones already replaced. You can take belt off and spin the items for feel and sound or use a stethescope - WARNING WITH THAT AS IT IS DONE WITH ENGINE RUNNING WITH MOVING PARTS OF COURSE but it is very effective.

A/C clutch bearing would be intermittent if bad and either make noise or not whether A/C is on or off. When off the clutch is just a pulley with a replacable bearing if caught early. Tensioners and idlers seem to take the most abuse over time. Rebuilt parts may have old bearings in them from the core they used........and some new ones can fail quickly too??!!

T
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/

Excellent Tom...

Just to add to Tom's..

Have you checked the belt tensioner as well?
No mention was made of that...just a thought..