330d weird noise

[Muhammede]

Hi guys. Just looking for some advice. Earlier today the fan belt snapped on my e46 330d.
I replaced the idler and tensioner pulley and also the belt with a continental belt (correct size), and started the car. It's now making a rattling sound on idle (like a knocking kinda sound) but after 900rpm the engine sounds normal again and drives properly. Smooth idle, normal power and everything works.
I put the old pulleys back but still the same rattle.
I have noticed that the belt is very jumpy on idle between the crank pulley and alternator but straightens out at 900+ rpm.


I'm lost here

Any advice will be highly appreciated
Thanks in advance

Sent from my D6503 using Tapatalk

 

[GoCart]

You might want to replace the tensioner itself.. could be the problem.

 

[Solo Man]

It is most probably the tensioner as that is prone to making the noise you describe when the belt is "lumpy". I have had it on me previous X5 and if you look at the tensioner you will notice the tensioner arm moving around as the belt circulates on the pulleys. My only conclusion is that the new belt either has a thicker section somewhere on its circumference that causes the tensioner to tighten and slacken as the belt goes around. I bought a new tensioner but never fitted it as as you say, the noise goes away when above 900rpm. The tensioner is spring loaded so should be ok as most of the time the engine does more than 900rpms.

 

[Muhammede]

I replaced the belt with one from bmw and the noise went away, but the tensioner was still wobbling alot. So replaced the complete tensioner and cup....n now the noise is back.

Sent from my D6503 using Tapatalk