Is my accessory belt misaligned, and if so, (how) can I fix it?

January 31, 2016 12:38 PM

I think my accessory belt is misaligned and/or loose. Can you confirm or advise? More info and pictures inside.

I got a new (refurb) alternator installed on Friday, and while the mechanic was at it, he also replaced the accessory belt. I drove the car on Friday and yesterday with no issues; the old alternator had a worn-out bearing and was very noisy, so the relative quiet was noticeable (and welcome). But today I started the car and immediately heard a new sound, kind of a regular harsh 'swishing' noise.

With the car running, I popped the hood to take a look. The sound was coming from the drive belt area, and this is what I saw: belt and power steering pump, belt and alternator.

Questions:
1. The belt is misaligned, right?
2. Can I drive safely with the belt like this, i.e., back to the mechanic? It's about 16 km.
3. Alternatively, can I fix it myself if I get a breaker bar or belt tool? (Store is about 5 km away.) I have sockets but nothing that allows me to budge the tensioner pulley bolt.
4. If I can fix it myself, do I simply loosen the bolt enough to centre the belt, and then re-tighten the bolt?

Thanks!

posted by methroach to Travel & Transportation (2 answers total)

Best answer: Yes, from your photos the belt looks misaligned - it's a ribbed belt, and it is off by at least one groove.

With most serpentine-type belts, there is one point of tension adjustment, but sometimes there are two. The game plan would be something like:

1. Locate and loosen the tension adjustment bolt.
2. Pivot that pulley inwards to reduce tension
3. Reposition the belt.
4. Pivot that pulley outwards to restore the correct amount of tension
5. Tighten the adjustment bolt.

Things to watch out for:

1. Make sure you don't accidentally connect the battery positive to ground (earth) with your pry bar or a wrench. Battery positive will be found on both the battery and one of the terminals on the alternator. So be wary of that, or at least aware of it.

2. Belt tension should be noted before you loosen the adjustment bolt, so you can restore it to the same tension when you're done. A typical belt tension is the ability to twist the belt long its length about 90°, i.e., you grab the belt between thumb and forefinger and push one edge down while pulling the other edge up. You should have about 90° of twist -- if you have less than that, it may be too tight, and more than that and it is already too loose.

Special note: Either this was installed incorrectly by the mechanic, or there's a problem with the belt's path such that it was installed correctly but moved after you started driving it. The first situation is bad, but the second is worse because it indicates a component is sitting out of alignment with the rest of the pulleys. Since the alternator is the newest component, it may be that you have the wrong alternator, or the wrong pulley, or the pulley is reversed on the alternator, etc. Do some followup after you adjust it and and make sure the belt runs true within its expected path.

Theere are two dangers with running it this way: shredding the belt, or having it jump off. Since it is being pulled inwards, shredding is more likely than jumping off. If it's squealing like a stuck pig, try to resolve this with minimal driving. If it makes noise but the noise isn;t ungodly, you can probably get away with driving it to either mechanic or parts store.

Good luck!
posted by mosk at 2:03 PM on January 31, 2016 [1 favorite]

Response by poster: Thanks, mosk! A lot of good and helpful information here. The noise isn't too bad--it really is just a non-squealing, rhythmic swishing sound. I'm going to get a belt tool tomorrow and follow your instructions.
posted by methroach at 4:09 PM on January 31, 2016