Engine makes sound when cold

[grig]

Hello bimmermen :)

I'm having the following problem.

Cold engine makes knocking-like sound for a few seconds when I start the car. It is 98' E39 M52B25TU.

My guess is that oil gets drained from some part of the engine. And then it takes some time to fill in and it makes the sound during that time. Do you know what it can be?

Thanks in advance.

[grig]

None has ran into similar problem?

[Dahab]

It could be too heavy engine oil, make sure you are using the right oil viscosity grade.
or Bad clogged oil filter
IF the oil warning lamp stays for a while it could be the oil pump.
Cheers

[grig]

It's not the oil. I changed oil twice (with oil filter of course) and it's the same.

[pizzaman09]

Does the M52B25TU have vanos? On all M62TU engines at some point the vanos system starts to knock making the engine sound like a diesel at start up.

[grig]

Does the M52B25TU have vanos? On all M62TU engines at some point the vanos system starts to knock making the engine sound like a diesel at start up.
Yes, it's double-vanos. Buf if it's the vanos unit, then why it shuts up completely after a few seconds?