After installing a car's timing belt and water pump, reinstall the alternator belt to the point where belt tension allows a one-half rotation twist. Tighten an alternator belt with tips from a certified auto mechanic in this free video on car engine repairs.
In this clip, we're going to talk about the proper service procedure to replace your engine's timing belt and water pump. In this step, we're going to talk about the proper procedure for reinstalling your engine's alternator belt. The first thing we're going to do is take and reinstall our belt idler pulley. Now we had to take this off in order to change our water pump. What we're going to do is just take and slip it back down in its mounting point and screw it down hand tight. All right. Once you have it ran down hand tight, you can go ahead and put your wrench on there and torque it down. All right and there you go. What I have here is the alternator belt and this one actually drives the alternator and the air conditioning at the same time. We're going to take and slip it over the crankshaft, which is the very bottom pulley. Now, if you can get it from the top, good. If you can't, you may have to get underneath the vehicle. All right, we got it around the crankshaft there and we'll take and loop it down around the air conditioning compressor now. Now that we have our alternator belt around our crankshaft, I'm going to take and slip it down and around the air conditioning compressor. All right. We're going to take and loop it underneath the idler pulley and over the alternator itself just like so. All right. Once we have it around the air conditioning compressor, we're going to take and go underneath the idler pulley just like that and over the top of the alternator just like so. If you have any questions or your belt isn't going on correctly, you're going to want to refer to your belt routing diagram. As you can see it says accessory belt routing, then it's going to have a configuration of directions that your belts go. Once you have your belts installed, then you can go ahead and tighten them up. This one happens to be a jacking screw style tensioner, which means it has a bolt I tighten up which is going to pull this alternator this direction. You can see that there. Watch the slop in the bolt right there. As I tighten this bolt up, it's going to pull the slack out of that belt. All right. The rule of thumb for any flat-style or serpentine-style belt, the tension you want on it is just enough to twist it one half rotation just like that. Once you have that tight enough, you can go ahead and take and lock down your mounting bolts. You have one here and an identical one in the back. And there you go. That is the proper service procedure for installing your alternator belt and tightening it down.