Buzzing sound in engine bay: which pulley(s) to check first?

Hey everyone, I’m reviving this issue, as I didn’t get much help when I posted a few months back, and this sound has been getting steadily worse.

It’s a buzzing sound, varies with engine speed, and sounds like it’s coming from the idler pulley (but it’s really hard to tell). Sounds the same (besides higher/lower pitch with RPMs) regardless of engine heat, running time, or gear. It’s to the point now that I can’t stand it and need to fix it. Before I jump into a massive project and diagnose all the pulleys, I wanted to check here and see if anyone has any ideas. Any help is appreciated

PS: how do I even check individual pulleys/components?

Link to vid with sound: https://imgur.com/a/60n7Bmc

Pull the intake system up to the plenum, pull the fan, pop covers off your tensioners. 14mm offset wrench to press down on the tensioners. Pull the belts. Pretty easy.

If you’re going to replace one pulley, might as well replace them all, and the belts.

Sounds like your power steering pump hates life. Any change to the sound when you turn the wheel?

spammysammich wrote

Sounds like your power steering pump hates life. Any change to the sound when you turn the wheel?

Nope, no change. Sound stays the same regardless of anything except engine RPM. I thought it was PS as well, but fluid level is healthy.

askjeeves wrote

If you’re going to replace one pulley, might as well replace them all, and the belts.

Does it sound like a pulley to you, and if yes, any one in particular? I have no problem replacing everything, just want to be sure first!

spammysammich wrote

Sounds like your power steering pump hates life. Any change to the sound when you turn the wheel?

I was under the impression that PS pumps do more of a moan/groan rather than a buzz when they're going bad or low on fluid. Is the PS pump the thing it sounds most like to you?

Stethoscope 🤷‍♂️

I’d bet one of your pump internals is shot. I don’t think that’s a pulley noise.

+1 on the stethoscope, that could help pinpoint which pump (or pulley) is screaming for life. Maybe harbor freight has a cheap one you can pick up.

Could also be something stuck in the the oil filter housing too.

Ordered a stethoscope, will arrive today and I'll try to pinpoint the problem area.

Ajolives wrote

I’d bet one of your pump internals is shot. I don’t think that’s a pulley noise.

+1 on the stethoscope, that could help pinpoint which pump (or pulley) is screaming for life. Maybe harbor freight has a cheap one you can pick up.

Could also be something stuck in the the oil filter housing too.

Got the stethoscope and went digging around the engine. I am almost positive that the power steering pump is the culprit.

Before I order one from FCP, are there any steps I should take to prevent this in future? The car has 70k miles, so I know parts do go out around this time, but is there some sort of filter in the PS reservoir that can get clogged or something? Don't want to install a new pump and starve it immediately!

Get the reservoir replacement kit from fcpeuro. The filter gets clogged over time and while it can technically come out on its own, I don’t think I’ve seen it available independently from the reservoir.

spammysammich wrote

Get the reservoir replacement kit from fcpeuro. The filter gets clogged over time and while it can technically come out on its own, I don’t think I’ve seen it available independently from the reservoir.

Thanks, I'll order that first and see if maybe the pump has been starved for fluid.

To be honest, I'm still confused as to why I am having none of the traditional power steering pump failure symptoms. Steering feels great, doesn't change with speed, the pump's sound doesn't change with steering angle. But the stethoscope almost certainly points to the PS pump making the noise. I've serviced many PS pumps over the years and not one has made this noise and been symptomless.

Alright guys, I checked again a little more in depth. The noise seems to be radiating to the PS pump, but the source is most definitely the oil filter housing. I changed the oil yesterday and was just in there, and nothing looked out of the ordinary AFAIK. I really don’t understand how the oil filter housing could be making a noise like this.

Any ideas? I am 100% sure that the noise is strongest there, so I won’t be giving conflicting information anymore…

Another post was made about this 6 years ago (https://www.m3post.com/forums/showthread.php?t=1663561) but he got no responses.

Maybe open up the housing, remove and reinstall the filter. It may not be seated properly. Also check the oil for debris, may be worth sucking out the oil and making sure nothings stuck at the bottom.

Ajolives wrote

Maybe open up the housing, remove and reinstall the filter. It may not be seated properly. Also check the oil for debris, may be worth sucking out the oil and making sure nothings stuck at the bottom.

Will do, ordered a turkey baster and will get in there tomorrow. I'll take some pics to ensure everything looks normal to you guys. Thanks!

Nice, good luck!

have the rod bearings been done for this car? If so, has the noise been happening since the job? it’s possible that the oil pump gear lash hasn’t been set properly. that would make a lot of noise in that general area.

spammysammich wrote

have the rod bearings been done for this car? If so, has the noise been happening since the job? it’s possible that the oil pump gear lash hasn’t been set properly. that would make a lot of noise in that general area.

Yup, rod bearings done by previous owner. Noise started happening shortly after I got the car, has steadily gotten worse. Stayed the same after this oil change. Only thing I’ve done to the car is this oil change and replacing the starter a few months back.

I found an example of gear lash but it sounds distinctly different than your buzzing.

oil pump backlash

spammysammich wrote

I found an example of gear lash but it sounds distinctly different than your buzzing.

oil pump backlash

That sounds like a real PITA to fix. Definitely does sound different from my noise, so that’s good.

Apparently at least one person has had this noise before, did you see the thread I linked a few posts ago? For context FYI, I got this car in January 2025, so this noise is relatively new.

Placing this here for reference, another post that has this sound. I believe this is the original video from the thread I linked above.

https://www.m3post.com/forums/showthread.php?t=1280293