Could a tune-up make a belt squeak suddenly?

I got a tune-up on my 2003 Toyota Matrix a little while ago. I was told that the serpentine belt would need to be replaced soon but all else was fine. When I started my car after the tune-up, the first thing I noticed was the sound of a squeaking belt, a sound that I did NOT hear before I dropped my car off. Occasionally, I’d hear a belt whine when the weather started getting wetter, but this was during dry times. The belt now squeaks regularly. My husband says that it’s normal for something like that to happen after a tune-up: parts that were going bad but were silent before will start to make noises. Is that true? Could a tune-up suddenly reveal the sound of a worn out serpentine belt? I’ve had it checked at another place and I know it does need to be replaced. I’m just wondering if I have reason to suspect tampering or if the tune-up guys are legit. Thanks!

“Tune-up” is a vague word. What work was done? It’s hard to help without that information.

They might have accidentally dripped oil or other fluids on the belt while working on your car.

Sometimes people become acclimated to their car, the ride, and various noises. After being serviced all of a sudden the ears perk up trying to find something wrong.

A tune-up (kind of a misnomer) should have no effect on a serpentine belt. You’ve been told by 2 facilities now that the belt needs to be replaced and the odds of someone tampering with a belt to make it squeak are about zero.

If the car has the original belt then it was likely in need of replacement long ago.

@matrixmama Here you go

I’m willing to believe this is the solution to your problem

It may be they had to loosen the belt as part of doing whatever it was they did for the “tune up”. And they then noticed the belt was on its last legs, so they told you about it. On my Corolla there is not need to loosen any belts to do a tune-up consisting of changing the spark plugs, the air filter, and checking the timing. But “tune-up” could mean anything, and include some activity where a belt might need to be loosened, such an a battery and charging system test. So while it is probably a coincidence, such a thing is possible.

It is not normal for a serpentine belt to squeak after a “tune-up” and I can see where you would be suspicious that something was tampered with. The only thing that doesn’t fit here though is that unless they have an exorbitant markup on a belt, there just isn’t much profit margin there.

Now a dishonest mechanic would have told you that you needed a new transmission or something on that order, then do a little tampering. That is where the real money is.

I think the belt squeaking is just coincidence in this case.

In order to inspect the belt, they may have taken it off partially and have operated the tensioner. The tensioner may now be a problem but you need the belt anyway so get a new one and if the problem is still there, you may have to spring for the tensioner.

Possibly the belt was removed to gain access to something and reinstalled in the opposite direction. A worn serpentine belt will often get noisy when the direction is reversed. Also, shops sometimes spray a belt dressing on a belt in an effort to isolate a noise and while the dressing will often greatly reduce a belt squeal momentarily, it can actually cause a belt to begin squealing or squeal louder a few miles down the road.