Knocking engine noise: mains?

[bgp001]

Well, this seems to be a part 2 of my story.

Changed the rod bearings about 12K miles (2 years) ago.
See this thread for details: https://www.m3post.com/forums/showthread.php?t=1513503

And this week after coming home I noticed some weird knocking noise.
I went for a drive around the block to record the sound with the phone on the cowl.

UPDATE 9/21:
No debris or metal in the oil filter, no glitter in the oil from the oil filter housing
No OBD codes
Couldn't find any source of rattles in the engine bay, yet to check the car from underneath

Car is currently parked, didn't start it since last week
---

What do you guys think?

[bvrider1]

0:07 secs sounds like rod knock
1:18 sounds like lifter or valve noise.

I am curious to see other people's response the the audio.

[NeverL8]

Originally Posted by bvrider1

0:07 secs sounds like rod knock
1:18 sounds like lifter or valve noise.

I am curious to see other people's response the the audio.

Heat shield? Didn’t feel like a rod knock to me

[bgp001]

I was concerned about noise at 0:28, 0:43 and it can be heard around 1 minute mark as well.
The drive was pretty slow and RPMs in 3-4K range.

Today I checked the oil filter housing and inspected the filter - no debris or metal, no glitter in the oil.

[bgp001]

Bumping this up in hopes to get more feedback.

Updated main post with more details

[Dpc2u]

It sounds like rod knock in the vid, but hard to judge by that. Another common source is the ac compressor. Sounds a lot like a rod knock. You could remove the belt and see if it goes away.

[bgp001]

Thanks, I've been thinking about A/C compressor too.
The sound is intermittent though, not sure if I'd be able to replicate it.
Going to try dropping the belt anyways to see if the bearing on A/C compressor is ok

[bgp001]

So I removed the A/C belt last night, compressor pulley has a tiny bit of play in it, don't think it's an issue.
The power steering pulley bearing seemed fine, but something inside the pump was making a weird clicking noise. Not sure if that's normal.
Here's the video (steering pulley first, then A/C compressor):

[tdott]

If you feel like that was causing the noise, then you'll have to start it up to see if the noise is still here.

Unfortunately anything short of removing the rod bearings to inspect them before starting the engine again could risk further damage if it is indeed rod knock.

Upto you if it's worth the risk to start it again without inspecting them.

[kimiraikkonen]

Originally Posted by bgp001

So I removed the A/C belt last night, compressor pulley has a tiny bit of play in it, don't think it's an issue.
The power steering pulley bearing seemed fine, but something inside the pump was making a weird clicking noise. Not sure if that's normal.
Here's the video (steering pulley first, then A/C compressor):

Hi. I think your A/C and Power Steering are driven off of the same belt (accessory). The other drive belt drives the Alternator and Water pump.

How many miles on your car. I recently had the Power Steering/AC belt go out (see pic below). The pulley looked like it imploded, which I assume took out the belt. I replaced both belts, pulleys, and tensioners and everything sounds a lot better. I think a lot of the clicks and squeals were coming from the pulley system. I have a MPE exhaust and I forgot how clean the induction sound is ....as before I was getting side squeals/clicks that were detracting from it.

[bgp001]

The car is just under 50k miles. When I took the belt off all pulleys as well as the tensioner looked good, so did the belt. No concerns there.
I guess I’ll try to start it without the compressor belt and then with it.
Not knowing what it actually is is really frustrating...

[bmwm3s65]

just from my experience, I am probably totally off but, it sounds very similar to a sound I was experiencing and what some users were describing as pre-detonation in this thread https://www.m3post.com/forums/showthread.php?t=1532390 due to being tuned. Is it possible, that the car was tuned when you purchased it? I just had the number 1 rod bearing spin in my engine and the sound was consistent and very specific and different what you posted and I had lots of glitter and metal flakes. Good luck. I hope you find the source of the sound and it's something inexpensive.

[bgp001]

Sorry for going quiet for a bit. Things got pretty hectic in the past two weeks

I've put everything back together after running the car with the serpentine belt off. Couldn't replicate the noise with or without the belt, unfortunately.

I also decided to take the car for a ride and the noise never came back. It's weird. I also had the car on the lift and tried to listen to noises at different rpms, but couldn't hear anything suspicious.

Originally Posted by bmwm3s65

just from my experience, I am probably totally off but, it sounds very similar to a sound I was experiencing and what some users were describing as pre-detonation in this thread https://www.m3post.com/forums/showthread.php?t=1532390 due to being tuned. Is it possible, that the car was tuned when you purchased it? I just had the number 1 rod bearing spin in my engine and the sound was consistent and very specific and different what you posted and I had lots of glitter and metal flakes. Good luck. I hope you find the source of the sound and it's something inexpensive.

Thanks bmwm3s65 for the suggestion to look at the pre-detonation/engine knock issue.
This seems to be a possible cause. Going to try running the highest octane fuel I can find and, maybe, some fuel system cleaner.