F30 engine noise

Hubu · 06-02-2023, 04:32 PM

Hi,

Engine: N47D20C

For a long time I am unable to eliminate a sound that comes from the front of the engine.

You can slightly hear it while it's running, but mostly when it's shut off.

I don't exactly know how to describe that sound (link below), but it sounds a bit like worn bearing - I want to hear your opinions on this.

Parts that were replaced with new ones during the search for the culprit:

Crankshaft pulley
Water pump
Alternator (45k miles) + new pulley
Compressor Clutch
Belt tensioner + belt itself

By discussing the topic on other forums and watching other videos on YouTube etc. I came across that in most cases it may actually be the crankshaft pulley - in my case it is out of the question, since the sound appeared before replacing the crankshaft pulley.

I don't want to unseal the compressor installation for nothing - in case it's not it.

Thanks for your attention.

Link: https://www.youtube.com/shorts/Pt3et1Sl-C4

Enabled · 06-02-2023, 04:55 PM

Do these cars have a one way clutched alternator pulley? (I'm surprised I hadn't looked into that before for N47)

My old VW TDI would do that noise against the belt when the alternator pulley was stuck and the momentum of the alternator would squeal against the belt as it slowed down.

But you did replace the alternator, so it can be assumed it is good.

Hubu · 06-02-2023, 05:01 PM

I'm not entirely sure.

The original alternator was from factory. The car's driven approx. 155k miles (250kkm).

It was replaced with another alternator that barely made 45k miles (only used part I've put in this car, hehe).

I've heard that the AC has several bearings inside, but I'm not sure whether the AC-compressors are known for failing or not

Enabled · 06-02-2023, 05:08 PM

I would try to locate the sound closely with a makeshift stethoscope like a large screwdriver pressed against the palm and next to ear.
If it's not around the alternator, at least you can move on to the next suspect.

Hubu · 06-02-2023, 05:23 PM

I've already been trying to locate this sound with a stethoscope. No sound from the AC, but I can't find any points to stick my stethoscope into on the crankshaft pulley...

The majority of people that have the exact same noise coming from this engine say that the crankshaft pulley was the culprit.

This was obviously replaced in my engine, but I still cannot say 100% that this isn't coming from it.

I have another theory confirming it cannot be the crankshaft pulley, and it was me starting the car without the serpentine belt on while the engine was still hot - and guess what, the engine didn't make a sound when it was turned off.

I hope that the pulley brand doesn't matter either...

Enabled · 06-03-2023, 07:05 PM

I have changed mine with Corteco.
They specifically say on them not to run the engine without a belt though. I wonder the reasoning behind that; possibly to avoid damage to the thick rubber part?

06-02-2023, 04:32 PM	#1
Hubu New Member 0 Rep 6 Posts Drives: F30 316D 2015 M-Sport Join Date: Nov 2021 Location: Somewhere iTrader: (0)	F30 engine noise Hi, Engine: N47D20C For a long time I am unable to eliminate a sound that comes from the front of the engine. You can slightly hear it while it's running, but mostly when it's shut off. I don't exactly know how to describe that sound (link below), but it sounds a bit like worn bearing - I want to hear your opinions on this. Parts that were replaced with new ones during the search for the culprit: Crankshaft pulley Water pump Alternator (45k miles) + new pulley Compressor Clutch Belt tensioner + belt itself By discussing the topic on other forums and watching other videos on YouTube etc. I came across that in most cases it may actually be the crankshaft pulley - in my case it is out of the question, since the sound appeared before replacing the crankshaft pulley. I don't want to unseal the compressor installation for nothing - in case it's not it. Thanks for your attention. Link: https://www.youtube.com/shorts/Pt3et1Sl-C4 Last edited by Hubu; 06-02-2023 at 05:05 PM..
	Appreciate 0 Tweet Quote

06-02-2023, 04:55 PM	#2
Enabled Lieutenant Colonel 1418 Rep 1,816 Posts Drives: 328xd Wagon, M2 Competition Join Date: Jun 2018 Location: Houston iTrader: (0)	Do these cars have a one way clutched alternator pulley? (I'm surprised I hadn't looked into that before for N47) My old VW TDI would do that noise against the belt when the alternator pulley was stuck and the momentum of the alternator would squeal against the belt as it slowed down. But you did replace the alternator, so it can be assumed it is good. __________________ -2014 328d Wagon, 8HP. Self-tuned, 270hp/430ft-lbs. -2019 M2 Competition MT, Alpine White. Self-tuned 560hp -2016 Mini Cooper S, MT. Many plans. Others: -E36 328is. 2000 Z3 Roady. 2003 VW Jetta TDI Manual. Estoril Z3M Coupe.
	Appreciate 0 Quote

06-02-2023, 05:01 PM	#3
Hubu New Member 0 Rep 6 Posts Drives: F30 316D 2015 M-Sport Join Date: Nov 2021 Location: Somewhere iTrader: (0)	I'm not entirely sure. The original alternator was from factory. The car's driven approx. 155k miles (250kkm). It was replaced with another alternator that barely made 45k miles (only used part I've put in this car, hehe). I've heard that the AC has several bearings inside, but I'm not sure whether the AC-compressors are known for failing or not Last edited by Hubu; 06-02-2023 at 05:06 PM..
	Appreciate 0 Quote

06-02-2023, 05:08 PM	#4
Enabled Lieutenant Colonel 1418 Rep 1,816 Posts Drives: 328xd Wagon, M2 Competition Join Date: Jun 2018 Location: Houston iTrader: (0)	I would try to locate the sound closely with a makeshift stethoscope like a large screwdriver pressed against the palm and next to ear. If it's not around the alternator, at least you can move on to the next suspect. __________________ -2014 328d Wagon, 8HP. Self-tuned, 270hp/430ft-lbs. -2019 M2 Competition MT, Alpine White. Self-tuned 560hp -2016 Mini Cooper S, MT. Many plans. Others: -E36 328is. 2000 Z3 Roady. 2003 VW Jetta TDI Manual. Estoril Z3M Coupe.
	Appreciate 0 Quote

06-02-2023, 05:23 PM	#5
Hubu New Member 0 Rep 6 Posts Drives: F30 316D 2015 M-Sport Join Date: Nov 2021 Location: Somewhere iTrader: (0)	I've already been trying to locate this sound with a stethoscope. No sound from the AC, but I can't find any points to stick my stethoscope into on the crankshaft pulley... The majority of people that have the exact same noise coming from this engine say that the crankshaft pulley was the culprit. This was obviously replaced in my engine, but I still cannot say 100% that this isn't coming from it. I have another theory confirming it cannot be the crankshaft pulley, and it was me starting the car without the serpentine belt on while the engine was still hot - and guess what, the engine didn't make a sound when it was turned off. I hope that the pulley brand doesn't matter either... Last edited by Hubu; 06-02-2023 at 05:29 PM..
	Appreciate 0 Quote

06-03-2023, 07:05 PM	#6
Enabled Lieutenant Colonel 1418 Rep 1,816 Posts Drives: 328xd Wagon, M2 Competition Join Date: Jun 2018 Location: Houston iTrader: (0)	I have changed mine with Corteco. They specifically say on them not to run the engine without a belt though. I wonder the reasoning behind that; possibly to avoid damage to the thick rubber part?
	Appreciate 0 Quote