BMW 520i why engine sound like diesel engine is it normal?

[Viper Warrior]

In year 2014 when the LCI comes in, not sure is it better insulation, the "diesel" sound was solved. No more "tiak tiak tiak" sound in cabin, only when you stand outside or open the bonnet, then you will hear it.

 

[TezzaRed]

What I've learnt through checking on other Bimmer forums overseas is that the diesel-sounding cold start is likely due to the timing chain wear & tear - and it usually goes away after some time (i.e. engine warms up). You will need to check on the timing chain assembly and possibly replace the guides.

Here are two videos that might be informative:
1. - N20 engine rattling
2. - N20 timing chain & guide replacement