Rattle in Engine, any thoughts?

[Bogdon]

2001 540i. Rattle on cold start up that lasts for a few second and then gets quieter. Progressively getting worse.

I can only compare the sounds to something I am more familiar with.

The cold start rattle sounds much like what an old small block chev sounded like when it had a lifter knock, like when the engine sat over night and the lifters lost oil pressure. Since the 540i motor is an overhead cam motor (I think) this is not possible.

When warm there is still a slight unusual noise heard. Like of like when the camshaft bearings in an old small block chev wore out, kinda of a soft, oil starved, slow knocking.

Other than these noises the engine seems to run perfectly.

Any thoughts?

[tomski]

Hello. The rattle you are hearing is most likely the timing chain tensioner. I would recommend changing the tensioner if it's still the original one. The tensioner has a back-up spring to apply the pressure against the timing chain rails, and over time the spring looses it's tension.

I also have a 01 540i and changed the tensioner. It helped with the noise, but from time to time I still hear a little rattle.