I ran back to the bus, applied some WD-40 along the length of the belt, and fired up the engine. The noise was gone, so I ran back inside to order a new belt (068903137D) from the Bus Depot. To save on shipping, I tossed in a couple other items. Within a week, the package arrived and I was ready to change my first fan belt.
Although I have four different repair manuals, I couldn't find instructions with enough details to help me with this process. I found a few posts on TheSamba describing the process of replacing the belt, here's my interpretation (Thanks to Amskeptic for filling in the important details):
- Remove the three 10mm bolts that hold the fan cover.
- Remove the fan cover and timing scale (behind the fan cover).
- Carefully pry the plastic alternator cover plate off by using a screwdriver at the top.
- Carefully loosen the 6mm hex bolt on the alternator. Do not remove the bolt or the back will fall off.
- Loosen the 13mm pivot bolt on the alternator, accessible from under the bus, in line with the oil dipstick. It took me a while to find this bolt until I used a flashlight.
- To loosen the belt, move the alternator to the left, pushing by the 6mm hex bolt. I had to carefully use a large screwdriver to apply enough pressure.
- Remove the old belt.
- Install the new belt. I found it easier to start by placing the belt on the alternator, and then slipping over the air intake fan.
- Tighten the belt by moving the alternator back to the right. I had to carefully use a large screwdriver to apply enough pressure. The belt should have 9/16” movement when pushed in the middle with your thumb.
- Tighten the 6mm hex bolt to no more than 10 ft. lbs. Do not overtighten this bolt.
- Tighten the 13mm pivot on the alternator to 15-20 ft. lbs.
- Replace the alternator cover plate.
- Replace the timing scale and fan cover, and then tighten the three 10mm bolts that hold the cover. Do not over tighten them or the timing scale or fan cover could crack.