Cold start rattle 2-3 seconds then gone.

[Slideways]

Update, started it today, first time it was ok after priming the system. Let it sit for a minute whilst getting the spark plugs in etc. And rattle is still there so I honestly have no idea.

perhaps something with the rocker arms or something but I’m not sure.

Maybe this is just normal I have no idea

Take a video of the noise.

[r3_galek]

Update, started it today, first time it was ok after priming the system. Let it sit for a minute whilst getting the spark plugs in etc. And rattle is still there so I honestly have no idea.

perhaps something with the rocker arms or something but I’m not sure.

Maybe this is just normal I have no idea

[jayjaya29]

Chain loosens up over time and the tensioner can't keep the slack under control so it rubs the pickup tube.

[beemer_guy]

#2 bearing just shows copper so I don't think the rod bearings condition is the cause for the rattle noise.
As about the chain cut on the oil pump intake tube, the engineers did a bad job design the tube as they have been in the business long enough to foreseen this, and reshape the tube away from the oscillating chain.

How in the world does that happen? The chain loses tension or something?

[sapote]

will send an update if the rattle has been fixed.

#2 bearing just shows copper so I don't think the rod bearings condition is the cause for the rattle noise.
As about the chain cut on the oil pump intake tube, the engineers did a bad job design the tube as they have been in the business long enough to foreseen this, and reshape the tube away from the oscillating chain.

[r3_galek]

Hi everyone, I’ve just done my rod bearings and found 2 things that could’ve been the sound. Cylinders 2 was quite worn as also copper was visible on 5, so it could’ve been the bearings knocking on startup potentially? Other thing I noticed was the cut on the oil pump from the oil pump chain, I’ve added an extra leaf spring from a new tensioner as don’t fancy taking the engine apart yet to replace the tensioner and likely stretched chain.

Crank also seems fine, measured with plastiguage and all within spec.

I’ve not started the engine up yet as I’m waiting on a few bits I found whilst taking it apart like, wishbone that was finished, water pump had a little play etc. So hopefully can get it running this weekend so will send an update if the rattle has been fixed.

[sapote]

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

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

[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]

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.

[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.

[jayjaya29]

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

[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]

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]

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

[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.