Left Hand. Size 50 Torx
Remove your idler pulley first. it is the pulley right next to the alternator.
The idler pulley is between the alternator and the A/C compressor.
M10 x1.50
The idler pulley on any vehicle is used to maintain the proper tension on the vehicle's belt(s). without it belt maintenance would be difficult.
Which pulley?
Remove serpentine belt. Remove pulley. Install new pulley. Install serpentine belt.
The idler tensioner pulley on your 1999 Ford F3 50 pickup truck is held in place with a single retaining bolt. The retaining bolt will go through the middle of the pulley. Tighten the retaining bolt to install the tensioner pulley.
you have another pulley and that the tensioner pulley and it is spring loaded and it keeps the belts and pulleys tighten .If its bad it will cause that sound
replace the belt with a goodyear bet
You adjust the idler pulley. It needs to be done by an expert, or it will shred.
The A/C compressor is located on the bottom of passenger side of the engine. It is the unit between the crankshaft pulley and the idler pulley. It is driven by the serpentine accessory belt.
Probably the serpentine belt idler pulley bearing.