[RESOLVED] Trying to Identify Engine Rattling Noise. Video Included

[aptwave]

Hello everyone,

Few days ago, after stopping my M3 E92 in front of my garage I heard this weird rattling sound comming from engine bay.

It is really hard to hear it, except you sitting near the front of the car. Sound is comming from passenger side. I also unable to find similar sound on YouTube or here on M3Post, so decided to create new thread.

You can hear it clearly from the begining of the video, dissapears at 0:08, when I moved phone little bit higher, and appears again at 0:17.

Anyone heard something similar before? I hope this is one of the pulley, and not something bad, like VANOS or some issue with engine head.


UPDATE - 17 Jul 2018:

So the issue was with tensioner pulley on A/C, power steering side. Replaced both pulleys, replaced belt and everything sounds really quite.

Original BMW pulleys can be replaced with INA - less money to spend, same pulleys as in original boxes.

[deansbimmer]

Could be a pulley, or the AC compressor. See a shop who can use an electronic stethoscope to isolate the source (or buy one on Amazon and DIY).

[aptwave]

Originally Posted by deansbimmer

Could be a pulley, or the AC compressor. See a shop who can use an electronic stethoscope to isolate the source (or buy one on Amazon and DIY).

Thank you for advice.

Bought stethoscope today and tried it on pulleys - bottom one sounds bad. Other spinning things sounds good, there's also no sound without belt so it is not from inside of engine.

Removed top and bottom pulleys and found that bottom one, with tensioner, has some noise when spinning it by hand, using stethoscope sound patters looks similar to my issue.

Going to replace it, pretty sure it will help.

[Scharbag]

I am chasing a strange rattling sound that comes and goes (for over a year) from the engine bay.

IT is effected by RPM but it is not present very often. Seems to be more prevalent at very low RPM and it is not consistent.

Today it happened as I parked the car - could reproduce for only about 20 seconds and then it went away...

Wondering if it is the A/C? Pretty sure it is not engine related as I have ripped on this car a lot in the last year and the noise, when there, has been pretty consistent.

Just wondering if anyone has some experience with this? Not meaning to thread jack but it seemed reasonable to ask this here instead of creating a new thread.

Thanks in advance!

[Scharbag]

Follow up - my noise was a borked supercharger bypass valve.