All The Horrible Things You Should Never Use To Quiet A Noisy Engine Belt

There’s nothing quite like being the smartest one in the garage. You know, like when you hear a squeal under the hood and your buddies are jumping immediately to nonsense like “recommended maintenance intervals” or “properly addressing underlying problems.” You know better, though. Because who cares *why* your belt is screaming like a printer with a paper jam, when there’s almost nothing easier than reaching for a can of belt dressing spray or — as we learned by digging deeper into car forums than we ever care to again — any number of other strange and inadvisable solutions. Well, it turns out that belt dressing is a lot like salad dressing: it doesn’t belong under the hood of your car. And the other off-brand solutions we found researching this were more or less all downhill from there. So let’s walk you through some of the bad automotive instincts when it comes to shutting up a noisy belt, and then get into what you should do instead.

To state the obvious, the noise isn’t the problem. It’s a symptom of the problem. A squealing or chirping engine belt often signals misalignment, worn pulleys, a weak tensioner, or some form of contamination. Masking the sound, whether it’s by grabbing some spray or turning the stereo up, will not only keep you from addressing the underlying issue, but could actually make the problem worse. (To be fair, the stereo solution does not, in fact, make anything worse, except maybe the riding experience for passengers, and that’s highly dependent on your taste in music.) In any case, like using your oil change reminder sticker to cover up that check engine light, masking the problem isn’t solving the problem. Besides, didn’t we already try to warn you about sounds that could mean your water pump is failing? Considering that’s one of maybe a dozen reasonably likely and potentially catastrophic mechanical scenarios, digging a little deeper is going to be worth the effort.

Just to be clear, the old-school wrench wisdom of just spraying some belt dressing and moving on with the day didn’t just come out of nowhere. So it’s with all proper respect that we concede “just spray it” as, once, a fairly legitimate solution to a squeak, chirp, or squeal under the hood. Old V-belts would indeed just get noisy and annoying sometimes, and giving them a quick spray actually *was* the right thing to do. So when a grizzled old mechanic with a heart of gold (or the cocky young apprentice with a cheek full of chew) tells you to use some spray, it’s at least partially because that used to be a pretty solid answer. Unfortunately, neither one of those guys is going to want to hear you lecture them about EPDM synthetic rubbers and how they’re engineered for dry operation under proper tension, so you might have to just nod attentively and then try to shift the topic to the virtues of Sea Foam.

Okay, just because those old heads don’t want to hear about the EPDM distinction, doesn’t mean that you don’t. ​​EPDM stands for Ethylene Propylene Diene Monomer, which is a type of synthetic rubber. Like so many automotive innovations that have made it considerably harder to work on your own vehicle, EPDM belts use modern materials and engineering to outperform their simpler, less technologically optimized predecessors: the humble neoprene compound. In exchange for being slightly more of a diva to work on, an EPDM belt is going to have higher resistance to heat and deterioration, leading to a longer service life and more consistent performance over time. One minor point of interest is that they don’t tend to crack and snap, but rather wear down gradually. This gives you a fighting chance at noticing any issues before you end up stranded, provided you take the time to inspect them now and then. Anyway, you can rock these things for 100,000 miles or more, especially if you don’t compromise their integrity by doing something stupid. Oh, and speaking of that…

So while we feel pretty confident in our assessment on why old timers are always reaching for that spray bottle, we’re a little more troubled by the variety of other “life hack” style solutions to this problem that persist out there in the automotive zeitgeist. For every “How do I fix a squeaky belt??” forum thread, there’s at least a couple of generally inadvisable solutions delivered with the kind of flippant confidence you can only find in an anecdotal internet comment. We’re not saying you’ve run across all of these in the wild, but we’re willing to bet you’ve encountered one or two:

RTV Sealant

• What it is: A liquid gasket product that you’ll tell yourself is a temporary fix
• What it’s for: Short-term sealing for oil pans, timing covers, thermostat housings, etc.
• Why it isn’t fixing your noisy belt: It’s literally designed to cure things into place, which is pretty much the opposite of what your belt wants to do. It’ll gum up your pulleys and ruin the belt. 

Brake fluid

• What it is: Hydraulic fluid made to transfer force to your braking system
• What it’s for: Brakes
• Why it isn’t fixing your noisy belt: Perhaps it isn’t as explicitly contrary to the intended solution as that sealant up there, this stuff definitely wasn’t made with smearing it on your belts in mind.

Zip-Ties

• What it is: Those little plastic guys that tie things up nice and tight
• What it’s for: Janky body panel repairs, hostage situations
• Why it isn’t fixing your noisy belt: The idea here is that you can shore up a weak tensioner arm or otherwise lean on the geometry of your pulleys, but this is a short-term solution even by automotive zip-tie standards.

Sandpaper

• What it is: Gritty and abrasive
• What’s it’s for: Smoothing out the birdhouse you just made
• Why it isn’t fixing your noisy belt: The recommendation here is that you use it to scuff up your pulleys, but intentionally damaging a perfectly good car part is usually reserved for things that don’t need to spin at 5,000 RPM.

The one thing that all of these approaches has in common is that they’re all trying to be just a little too clever for their own good. Since around here we like to avoid too much creativity under the hood and stick to simple acts of maintaining your car, let’s keep this moving.

Not every misguided repair involves zip ties or woodworking techniques. Here are some more grounded approaches that you still shouldn’t touch with a ten foot breaker bar:

• Belt dressing sprays: We opened with this one earlier because it’s kind of the godfather of bad solutions to this problem. The bottom line is that these were meant for old neoprene V-belts, not modern EPDM serpentine ones. The tacky coating in the spray attracts grit and accelerates wear.
• Lubricants: This includes WD-40, and please choose literally any other website if you want to argue about that in the comments. Regardless, this might create instant quiet, but you’re also introducing additional out-of-spec slippiness that’s doubtlessly making the problem worse, even if you can’t hear it anymore.
• Wax or bar soap rubs: This is the same basic deal as above, but you’ll feel slightly more sophisticated since it isn’t coming from a can that you fished out from underneath the passenger seat. Soap and wax will melt and smear across pulleys, changing the belt’s frictional characteristics and collecting grime.

It’s all bad news, is the point. The bottom line is that if something changes the surface of the belt (or the pulley) instead of actually dealing with what’s going on around it, you’re not addressing the problem.

Dressings or lubricants can swell ribs, glaze pulleys, and attract grit, leading to more slip and noise. Major parts suppliers explicitly warn against it, and we’re pretty sure that’s not just because they’ve all been compromised by some sort of dark money special interest group backed by greedy mechanics hellbent on extracting those sweet, sweet tensioner adjustment dollars from savvy and creative DIYers. So even though we pride ourselves on recognizing and advocating for the bare minimum of car maintenance, we’re going to encourage everybody out there to err on the side of reliability and help you not only avoid gunking up your works, but also to direct your attention to the actual problem that may, as we’ll get to in a second, be no big deal after all. Of course, even if it *is* a big deal, that makes for more reason to get it addressed, not less.

Here’s the thing. If your belt’s making noise, there’s an actual reason for it, and none of those reasons are that you haven’t yet found the right internet remedy involving vise-grips or equal parts transmission fluid and tomato paste. Fortunately, a little poking around might help you get to the bottom of things. Start simple. Pop the hood and check the belt’s condition. You’re looking for cracks, shiny glazing, or missing ribs, with any of the above meaning it’s time to work on getting a new one in there. If the belt seems okay, turn your attention to the tensioner. Does it wobble, bounce, or feel weirdly gritty when you spin it? You might be onto something. Another possible culprit? Pulley alignment. One bent bracket or questionable alternator installation with a slightly askew pulley can yank the whole setup out of step. You may have noticed that none of these scenarios sound like the kind of thing that can be addressed with creative use of fluids.

There’s a fine line between “just a squeak” and “hey, is that smoke?” — and you usually find it about two days after deciding to ignore the problem. If your belt ribs are swollen, your tensioner bearings feel gritty, or one of your pulleys wobbles, that noise that started you down this road in the first place was trying to tell you it’s time for attention. Masking the sound with spray (or anything else along the spectrum of automotive jankiness detailed previously) doesn’t just avoid the issue, but can actively accelerate failure by trapping heat, accumulating grit, and weakening the compound of the belt. In any case, you may or may not feel comfortable doing the work yourself, but there’s an excellent chance that you’ll feel like a pro in working through the diagnosis. (This could be like when you got a little cocky after you learned how to read the oil level on a dipstick correctly a while back.)

Sorry, but more often than not, this issue isn’t going to have a solution from the parts supply shop shelf, but perhaps from behind the parts supply shop counter. So close and yet so far, you know? But it’s likely that the correct fix is as boring as it is effective: replace what’s worn, clean what’s dirty, and don’t improvise. If you get lucky, maybe you don’t even need to replace the belt at all. But if you do, just be sure to use an OEM-spec belt, make sure every pulley surface is oil-free, and check the tensioner and idler bearings for roughness or play. If there’s any sign of fluid contamination, fix the leak before the new belt goes on—otherwise you’re just giving it a head start on its next complaint. Once you’ve built some confidence in finding your way around a serpentine belt, you can go ahead and add this to the list of car maintenance items you should probably check on from time to time. Besides, nothing feels quite as smugly satisfying as popping the hood, seeing everything spin in perfect silence, and knowing you fixed the real problem instead of creating a new one.