E46 320d knocking sound on idling

[Tyx]

So my 2002 E46 320d had this irritating knocking sound(Like the old diesel bakkies) when it is idling. This has been going on for the last six months as I could not figure out where the noise was coming from. The noise would go away when the revs increase. Could trace it to the front left side of the engine(near EGR) but could not pinpoint the exact location.
Turned out to be the tensioner pulley(bearing and back piece).
The mechanic that fixed my car when the oil cooler leaked through picked it up. When they changed the defective parts the noise actually got louder and we then found out that the damper pulley rubber was cracked. This was an aftermarket pulley which was off centre. So the reason why the knocking sound was there in first place was the aftermarket damper pulley thatis not made according to oem spec. It is a bit of centre which means the tensioner pulley must work harder to keep the belt tesioned and thus get broken quicker.

Just thought I share an expensive lesson. Don't buy the aftermarket damper pulley adfvertised on Gumtree.:idea:

 

[P1000]

I read the first paragraph and thought it is most likely dampener pulley...

I agree for a part that is so critical, rather make sure you buy the best you can afford. The stealers want silly money for that part, so I'm not sure where you would go next. Maybe post up the details of the supplier if you have found a good quality part for a reasonable price.