Owners of 2007-08 Ford Explorers, Explorer Sport Tracs and Mercury Mountaineers, as well as 2009 Ford Mustangs (all with 4-liter engines) may complain of a squeal or chirp from the front of the engine. Two likely causes for the noise, Ford Motor Co. said, are a defective or misaligned accessory drive belt.
To determine which issue you're up against, start by opening the hood. Using the illustration, measure the gap between the rear flange of the idler pulley and the drive belt, as shown. The gap should be approximately 3/32nd inch. If it is, the drive belt is properly aligned. Just replace the belt with an upgraded design (part No. 9L2Z-8620-A for the SUVs; part No. 5R3Z-8620-AA for Mustangs) and the noise should be eliminated.
If the gap is less than 3/32nd inch, you're dealing with a misalignment problem. Before doing anything, try loosening and retightening the alternator bracket and idler pulley bolts to spec, then remeasure the gap between the idler pulley rear flange and belt.
If the gap is now within spec, replace the drive belt with the upgraded part and the fix is complete. If the gap is still less than specified, the alternator bracket is likely bent. Replace it with a revised unit, part No. 1L5Z-10A313-BA, then install the upgraded drive belt.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via e-mail at [email protected].