[Olihoward]

So i recently rebuilt my engine after a spun rod bearing. No issues until i started up and there was a small intermittent buzzing noise around the front of the engine. The noise is only on idle, the car revs and drives no issue. however the noise becomes constant on idle once the engine is warm.

my only ideas are timing chain is catching on a guide, serpentine belt tensioner is wobbling or alternator pulley is done.

Currently at work for two weeks without the car so stuck thinking of ideas without been able to test them.

2016 m135i
Any ideas ?

https://youtube.com/shorts/F4mgIHBWLeE?feature=shared

[skitsos]

Have you found what could be the root cause of this?

I noticed the same buzzing noise, coming from front of engine, on my '14 M235i (67k miles). I started the car this morning and went inside to let it warm up for a bit like usual. Then noticed the noise when I came out a few minutes later to leave for work. The car seems to run just fine, and throws no codes. Buzzing noise was still there when I pulled into a parking spot at work (short ~5min drive, but oil temp was over 160F at this point). After work I will listen to see if it also produces the buzzing noise immediately on cold start...

I should also mention that a few months ago I replaced the valvetronic actuator, eccentric shaft, valve cover, gaskets. PCV is operating as it should. Next I plan to check if the noise continues when the serpentine belt is removed (I have to replace belt, pulleys and tensioner anyway)... but I've also heard that the following could also be the source of the buzzing noise (which I plan to check next if the belt/pulley/tensioner change doesn't resolve this):

- Oil filter housing basket (that the filter wraps around) disconnects from cap.

- Faulty Vanos solenoid (located at front of cylinder head, which sounds like where the buzzing noise is loudest...)

- Faulty thermostat and/or water pump