Cold start rattle 2-3 seconds then gone.

[ac427]

I don't think this is tensioner related, I believe i have the same rattle, rebuilt the vanos, replaced the tensioner with a brand new one from BMW, chain guide from beisan and it still persists.

I'm not sure what is left apart from bearings.

[ac427]

Perhaps the oil pump is getting tired. I believe they have an O-ring on a piston within them, that regulates oil pressure output.

[jayjaya29]

Perhaps the oil pump is getting tired. I believe they have an O-ring on a piston within them, that regulates oil pressure output.

You're grasping at straws. The o-ring is tightly constrained and is not a source of failure.

[ac427]

You're grasping at straws. The o-ring is tightly constrained and is not a source of failure.

Maybe, a friend replaced his during a rebuild.

My oil pump has done nearly 200k miles.

What do you think it could be?

[jayjaya29]

Rod bearings, check the oil pump while you're in there.

[r3_galek]

Could be early signs of rod bearings going out as replacing them seem to have fixed the issue for Andratch, I was planning to do mine anyways in the coming weeks, just need a couple final bits. Hopefully that fixes it, if not I am completely lost. Will post an update once that is done.

[sapote]

Maybe, a friend replaced his during a rebuild.

My oil pump has done nearly 200k miles.

What do you think it could be?

then put a P gauge at the oil pressure sensor to see its pressure during starting to nail down if it's normal or delay with low oil pressure.

[Josep_BP]

The same thing happened to me two years ago when I changed the connecting-rod bearings. The BMW mechanic fitted them incorrectly and there was a squeaking noise for two or three seconds, after which everything ran smoothly. Luckily, I asked the mechanic to check it thoroughly, because that wasn’t normal, and sure enough, the connecting-rod bearings had been fitted incorrectly and had started to wear out after just 500 km. The noise was like two pieces of metal rubbing together.

[sapote]

. The noise was like two pieces of metal rubbing together.

This is no good for the crank journals -- no damages on them?