Serpentine belts

I had some work done on the Cherokee over the weekend. Monday I turned on the a/c and there was a squeal that sounded like a giant sqealing thing. I turned it off and went back to the shop. The kid said that the belt was too tight. Ar? :confused: I thought the sqealing came because the belt was too loose; slipping. I had driven 80 miles to the shop, and when I turned the a/c on there it was silent. After the kid loosened the belt it was silent – until I started to leave. When I turned the wheel slightly it started up again. (Note: It’s my habit not to turn the wheel all the way to the locks, as I feel this puts a strain on the system. The squealing started before the lock.) He was going to soap the belt, but I suggested he tighten the belt instead of loosening it. He said that he’d never heard of such a thing, but decided to do it just to eliminate it as the cause of the slippage. No squeal. I turned the wheel to the locks (left and right) and there was no squeal. I turned the a/c on and turned the wheel to the lock. No squeal. It’s been quiet since he tightened the belt. It had him perplexed.

So what’s the deal? I, a non-mechanic, assumed that a slipping belt needed to be tightened. He, someone who works on cars all day, thought that loosening it was the solution. My non-professional intuition worked. But is the accepted remedy loosening the belt? Or was the kid just wrong from the start?

The kid was wrong. Squealing means either loose or perhaps glazed. How long has it been since the belt was replaced? Might be time to replace it.

I don’t remember when it was replaced, but ‘fairly recently’. The head mechanic (who was not there Monday) noted that it looked fairly new. I’m hoping that my not turning the wheel to the lock and not running the a/c when the belt was squealing helps to prevent glazing.

Related question: When does a ‘fan belt’ become a ‘serpentine belt’? Is a ‘fan belt’ one where all of the angles are ‘internal’, and a ‘serpentine belt’ has angles that are ‘external’?

You were right, the kid was wrong. Don’t sweat damage to the belt, it did last long enough to do serious glazing.

IIRC, a serpentine belt is one continuous belt, as opposed to having several belts, which my include alternator, fan, and power steering belts.

Checking wikipedia

Yes, and it’s thicker, too, so you can put more tension on it, leading to less slippage, for better efficiency and less premature wear.

Actually they are designed to run at a lower tension due to the greater surface area. This makes them last longer.

“The kid said that the belt was too tight.”
Bolding mine.

There are a lot of people earning money in auto service who are poorly qualified to do so. Chain operations especially tend to hire younger entry-level help (and then train them to sell rather than to have good mechanical judgment, but that’s another topic). Basically, this kid didn’t know his ass from a hole in the ground. Overly tight belts can overstress pulley bearings, but don’t cause squealing. Loose belts do. [editorial] This is what you get when you shop for cheap auto repair. [/editorial]

Fan belt is an old term for accessory drive belt. On older cars, the radiator fan (cum water pump) was one thing, and the most important thing, that was always belt driven. There might also be an alternator/generator belt, a power steering belt, an A/C belt, etc., but they were sometimes generically called fan belts.

In olden days, drive belts were V belts, shaped like the letter V with the point cut off. Then came multi-ribbed belts. These are flatter than V belts, grooved on one side. The grooves are actually a series of tiny V’s.

Then came serpentine belts, which as mentioned above snake in and out among several pulleys (4-7, usually), wrapping around some pulleys on the smooth back side of the belt. All serpentine belts are multi-ribbed belts.

Although some multi-ribbed belts simply wrap around 2 or 3 pulleys the way V belts do, and thus are not serpentine, virtually all parts and service people call them serpentine belts. Auto repair is not famous for inspiring careful and exacting use of terminology.

Yes, the kid’s wrong. I went through this with a Jeep Cherokee within the last year, a water pump and serpentine belt replacement and the belt needed tightening seven times. Being loose makes it skid over the pulleys like tires over the road, hence the screeching squeeling noise.

By the way, don’t use your belt tension gage on the belt while it’s running. An obvious maxim, you might think - but not so for one unlucky backyard mechanic. This belongs in a “stupid things people do” thread but it seemed harmless enough to stick it here.