In America, we have a certain vision of the SUV; our ideal is that an SUV should be the size of a Saturn V rocket, and have a V-8 engine with about as much power as the Titanic. Here, a four-cylinder SUV like the 4Runner is something between a joke and a mistake, to people who have never owned one. But I've always found that when it comes to off-roading, just enough is just right, and too much is usually way too much.
The 2.7-liter four-banger used in this 4Runner had three belts, arranged in sort of descending order of importance. The front belt ran the power steering pump pump on the top right. The middle belt ran the A/C compressor on the lower-left of the motor, and the rear belt looped around the all-important alternator and water pump.
Like a lot of older engines without self-adjusting belt tensioners, the 3RZ-FE used some of the accessories themselves as the tensioners. This is the case with the alternator, though the power steering and A/C belts use manually adjustable idler pulleys as tensioners. A lot of Toyota engines use industrial belt tensioning systems like this; the accessory swivels on a single bolt, but unlike old American cars, Toyotas like this use a perpendicular "jack bolt" to tighten the belt. The jack bolts are on the sides of the brackets, pointing toward the center of the motor.
I started by removing the plastic fan shroud's four bolts and pulling the shroud up and out of the engine bay. It was a bit of a pain wiggling it up around the fan, and I know this step wasn't technically necessary. But I like room to work, so out it came. I could have pulled the mechanical clutch fan off, too, but that's just more aggravation than it's worth.
Because I had to replace the rear belt, I went ahead and loosened all of the front-facing bolts on the power steering belt idler pulley arm, A/C compressor idler pulley arm and alternator. Those are the ones that lock the parts to the brackets. The power steering pump immediate swung down, but the alternator needed a little bump with a rubber mallet, and I had to break the A/C compressor loose by crawling under the truck and turning the jack bolt counterclockwise to push the compressor toward the motor.
Before putting the new belts on, I went ahead and adjusted all of the jack bolts all the way in by turning them clockwise. That gave some room for adjustment later, once the belt takes a set and stretches some. The new belts went on just like the old ones came off. After putting the rear belt over the alternator and water pump, I grabbed the alternator and pulled up hard. While hold the alternator up and the belt tight, I tightened the bolts hand-tight to hold the alternator in place. Then I went back and snugged the lock bolt on the top to 21 foot-pounds, and the pivot bolt on the bottom to 43 foot-pounds. At that point, it was just a matter of tightening the jack bolt until I had 1/2 inch of deflection when pushing on the middle of the longest span of the belt.
Then came the A/C compressor and power steering pump belts. The tensioner arm bolts took 48 to 58 foot-pounds of torque, and the belt tightening with the jack bolts was the same. With the belts on, I reinstalled the fan shroud, and just snugged its bolts up hand tight.