Cold engine noise is driving me insane.. seeeking help/suggestions

[m3f_MrChaos]

There is a tapping/knocking sound coming from my M3 (engine), which neither my father or I are able to isolate to a specific place. It seems that it is most pronounced if you listen from right under the front lip. The noise is louder and more consistent with dropping temperature. The VANOS, upper tensioner, main tensioner and upper timing chain have all been replaced already. When the engine gets warmed up, the sound nearly vanishes, and the car runs great.



We have deduced the following:

- The sound is at a slower rate than the engine speed itself, we are fairly sure. This gets rid of the possibility of rod knock or piston slap, unless my ears are lying to me.

- The sound SEEMS to me as if it's coming from the bottom front of the engine, or bottom of the engine. This leads me to believe it is in the oil pump or lower timing chain (possibly a broken or worn lower guide).

- Possibly a sticking valve or lifter.



Any input? We have already pulled all the belts, and the sound is still there, so we know it's in the engine. Currently running 0w-40 synthetic oil.



Thanks

-A

[m3f_CrazzyM3]

You've done alot of work on your car so far.......if i remember correctly this has been troubling you for a while now......at this point I would take it to a bmw service station and see what they have to say about it........have you done that already?

[m3f_Roadrunner_00430f3330]

mrchaos, looks like you've covered all bases. now time to see a certified bmw tech.