[AJ9x]

Background: 2011 335i, 78k miles, bolt on mods only, car still feels perfectly fine driving. Something under the hood is making a whine-type noise. It makes it at idle, or driving slow. Seems to go away with pressing the throttle, then comes back when I let off the throttle. Initially, I thought it to be the pulley assembly. Nope. Car shop said they felt it was coming from the torque converter, but I can't imagine that going bad at 78k mi. So I'm open to opinions from you guys before reputable shops open back up next week.

Here's a video that shows the noise that I just uploaded:

Has anybody experienced this?

[AM330i]

I don't think it's the transmission, I'm thinking maybe turbo's

[AJ9x]

Originally Posted by AM330i

I don't think it's the transmission, I'm thinking maybe turbo's

I took it in to a local shop just to identify the noise. They were the ones who said it was coming from the torque converter area. I just find it hard to believe transmission components failing after only 78k

[Corno_Baldwin]

Hard to know not being there.

I think it sounds like a pulley - take off the serpentine belt and feel the pulleys. Any loose or wobbly? Any make noise when you spin them?

Not sure if it a safe to start the cars without the alternator spinning, but perhaps starting the car without serpentine belt just for a few seconds. If sound isn't there that either rules out pulleys or trans.

I also don't think it's trans related.

[kkasson]

Originally Posted by Corno_Baldwin

Not sure if it a safe to start the cars without the alternator spinning, but perhaps starting the car without serpentine belt just for a few seconds. If sound isn't there that either rules out pulleys or trans.

Should be fine to start it without the belt - it will drain the battery but you should be fine to run it for ~20 or 30 seconds with no belt.

[AJ9x]

Originally Posted by Corno_Baldwin

Hard to know not being there.

I think it sounds like a pulley - take off the serpentine belt and feel the pulleys. Any loose or wobbly? Any make noise when you spin them?

Not sure if it a safe to start the cars without the alternator spinning, but perhaps starting the car without serpentine belt just for a few seconds. If sound isn't there that either rules out pulleys or trans.

I also don't think it's trans related.

I need to do this myself. The car shop swore it wasn't anything from the pulley assembly, but I also don't believe when they said it was transmission related.

[CTinline-six]

I also second the idea of pulling the belt and running for a few seconds.

The fact that you said it happens once the vehicle is warm makes me think a bearing in one of the pulleys is shot.

Did the shop do any diagnostics? If I go to a shop and they just point at major components saying they are the issue without doing any diagnostics, I usually walk away and never call them again.

[AJ9x]

Originally Posted by CTinline-six

I also second the idea of pulling the belt and running for a few seconds.

The fact that you said it happens once the vehicle is warm makes me think a bearing in one of the pulleys is shot.

Did the shop do any diagnostics? If I go to a shop and they just point at major components saying they are the issue without doing any diagnostics, I usually walk away and never call them again.

Pulley bearing was my very first guess. Did the water spray on the belt test, didn't change the noise at all.

They did no diagnostics, but at least I wasn't charged for anything.

[AviatorBimmerFL]

Turn the car on, take WD40 and spray both the tensioner and idlers. The noise will most likely dissipate this indicating a bad pulley.

[CTinline-six]

Originally Posted by AJ9x

Pulley bearing was my very first guess. Did the water spray on the belt test, didn't change the noise at all.

They did no diagnostics, but at least I wasn't charged for anything.

Yeah unless the belt is the actual problem the water won't do anything. Also, depending on how the bearings are sealed in the pulleys the WD-40 trick might not be 100%.

I would pull the belt, run it for a few seconds and see if that helps. If it does, then try the WD-40 trick to isolate which pulley it is, or spin them by hand to see which one feels rough or worn.

[AJ9x]

Originally Posted by CTinline-six

Yeah unless the belt is the actual problem the water won't do anything. Also, depending on how the bearings are sealed in the pulleys the WD-40 trick might not be 100%.

I would pull the belt, run it for a few seconds and see if that helps. If it does, then try the WD-40 trick to isolate which pulley it is, or spin them by hand to see which one feels rough or worn.

I have narrowed it to either a pulley or an air leak somewhere. Either way, not an expensive fix. Reputable car shop opens on Tuesday, I'll have to take it there for a definitive answer.

[e90ca]

This sounds exactly like what my 335i was doing a few weeks ago. But I was told that this is a cracked valve cover. There are a few threads about this as well.

[AJ9x]

Originally Posted by e90ca

This sounds exactly like what my 335i was doing a few weeks ago. But I was told that this is a cracked valve cover. There are a few threads about this as well.

Appreciate the suggestion, hadn't thought of that. I'm taking it to a good shop tomorrow. I'll ask them to give that a check. It makes the noise when my foot isn't on the accelerator, but when I give it gas, it goes away. The changes in air pressure would explain the sound/symptoms.

[Cory S]

Other videos on the forums points to a potential valve cover/PCV leak.

[AJ9x]

Originally Posted by e90ca

This sounds exactly like what my 335i was doing a few weeks ago. But I was told that this is a cracked valve cover. There are a few threads about this as well.

Looks like we have a winner here. I was told it was the PCV that has failed. Ordering a new valve cover and replacing it myself. The car shop quoted me at $1300 and I accidentally laughed out loud over the phone. ECS Tuning has the valve cover for $400 and the job should cost less than $500 total. It's an easy job, albeit tedious.