[Beisofmarko]

Hi,

My car has started this knocking sound after summer and it's been getting much worse as the temperatures drop towards winter.

Link to knocking sound: https://streamable.com/szjf41

Symptoms: Knocking starts 2-5 seconds after cold start, it speeds up if i raise the rpms.
Knocking at idle goes away after few minutes, and after driving a bit as the car warms up,
all of it goes away and won't come back untill next morning when doing cold start again.

I took accessory belt out and did cold start next morning and there was no knocking at all.
I couldn't pinpoint the culprit and only part that had some sort of slack,
was the alternator pulley but i changed that and sound came back after putting belt back.
Setting AC to full/off doesn't make knocking any different.

To my ear it sounds more alternator side that passenger side but it's hard to say.

Anyone had similar symptoms or ideas how to proceed?
2006 e92 n54.

Thanks!

[sabino56]

Sounds like when the OAP alternator pulley on my N52 failed but you replaced that already. Only suggestion would be to measure and find shorter belts to bypass accessories. I did that when trying to find the cause of my noise which turned out to be the OAP. Autozone has a lot of various length belts but not all carry everything so a pain to find the ones you may need. Good luck.

[SlowE92]

Originally Posted by Beisofmarko

Hi,

My car has started this knocking sound after summer and it's been getting much worse as the temperatures drop towards winter.

Link to knocking sound: https://streamable.com/szjf41

Symptoms: Knocking starts 2-5 seconds after cold start, it speeds up if i raise the rpms.
Knocking at idle goes away after few minutes, and after driving a bit as the car warms up,
all of it goes away and won't come back untill next morning when doing cold start again.

I took accessory belt out and did cold start next morning and there was no knocking at all.
I couldn't pinpoint the culprit and only part that had some sort of slack,
was the alternator pulley but i changed that and sound came back after putting belt back.
Setting AC to full/off doesn't make knocking any different.

To my ear it sounds more alternator side that passenger side but it's hard to say.

Anyone had similar symptoms or ideas how to proceed?
2006 e92 n54.

Thanks!

My 535xi knocks in the morning when its near freezing temperatures and under. In my experience it's normal and due to the cold temperatures and oil not warming up enough. I would just let the car sit for maybe a minute longer and or change oil to something with lower viscosity. Only happens in the winter. Hope that that helps.

[TheMidnightNarwhal]

Originally Posted by SlowE92

My 535xi knocks in the morning when its near freezing temperatures and under. In my experience it's normal and due to the cold temperatures and oil not warming up enough. I would just let the car sit for maybe a minute longer and or change oil to something with lower viscosity. Only happens in the winter. Hope that that helps.

My car has been used in -20c weather and never knocks. 5W-40 Pennzoil Euro used. Maybe you have top end "knocking", I know the lifters can be noisy when cold.

[TheMidnightNarwhal]

Yeah if the knocking is gone with belt off then it should be a pulley or accessory. That said I don't have much advice to actually pinpoint the culprit other than feeling pulleys by hand, but then I don't think you can spin the accessories pulleys by hand.

[SlowE92]

Originally Posted by TheMidnightNarwhal

My car has been used in -20c weather and never knocks. 5W-40 Pennzoil Euro used. Maybe you have top end "knocking", I know the lifters can be noisy when cold.

My 535xi is an old girl, 230k miles on engine. Have some piston slap. I should revise my previous statement.. If your engine has a lot of miles it could just be piston slap, but thats just the price with an older car.

[Beisofmarko]

Originally Posted by sabino56

Sounds like when the OAP alternator pulley on my N52 failed but you replaced that already. Only suggestion would be to measure and find shorter belts to bypass accessories. I did that when trying to find the cause of my noise which turned out to be the OAP. Autozone has a lot of various length belts but not all carry everything so a pain to find the ones you may need. Good luck.

Originally Posted by TheMidnightNarwhal

Yeah if the knocking is gone with belt off then it should be a pulley or accessory. That said I don't have much advice to actually pinpoint the culprit other than feeling pulleys by hand, but then I don't think you can spin the accessories pulleys by hand.

I'll get shorter belt (7PK1440) that bypasses lower idler pulley and AC pulley so i can rule ac compressor out.
I'll try to feel other pulleys by hand again.

Could it still be something wrong with alternator itself or it's shaft instead of it's pulley that i did change?

It's probably not coming from vibration damper as i would assume it should make some noise without belt aswell?

[TheMidnightNarwhal]

Originally Posted by Beisofmarko

I'll get shorter belt (7PK1440) that bypasses lower idler pulley and AC pulley so i can rule ac compressor out.
I'll try to feel other pulleys by hand again.

Could it still be something wrong with alternator itself or it's shaft instead of it's pulley that i did change?

It's probably not coming from vibration damper as i would assume it should make some noise without belt aswell?

Sorry I'm not that experienced with accessories but I also would think that the if it was vibration damper, it would also make the noise. Also it might not necessarily be a pulley like you say, it could be something internal to the accessory I assume.

But just to make sure, I would do more than one cold start without belt to really make sure it wasn't just a one off you know.