M104 noise from front top of engine - timing chain/tensioner?
 

My M104 makes a noise at idle which seems to come from the front/top of the engine. All aux stuff like alternator, AC compressor, belt tensioner etc. is working and not making any noise. This engine does not have an air pump.

The engine seems to work like normal, milage is normal, performance as well etc. The noise has been there as long as I've had the car..

Mileage is over 300000 km, that'll be close to 200k miles.

Can anyone help me pinpoint this problem?

Check the link here for a short video of the noise: https://youtu.be/Ia_Nniw0ZL4

When was the last time you had a valve job? I'm probably wrong(haha) but it sounds either like you need a valve adjustment or you're running low on oil. Then again you say it's only at idle so that might rule out valves.

change oil to see if metal flakes.Mine did that,i bought a newer engine.Never tore it down cause alumin all thru engine.Might be oil chain pump.

This engine has got hydraulic valve lifters as far as I know. Oil is perfectly fine, level correct, pressure good and oil/filter changed 1500 km ago. I've heard the same noise from another M104 engine, but then again another without any noise. It doesn't seem to impact anything, but it doesn't sound very good at all. The noise seems to disappear at higher revs and it's not possible to hear it inside. The video makes it appear worse than it is.

Many 104s have an audible piston slap at slower speeds and with the longer stroke of the 3.6 it can be exacerbated. Never seen a real problem come of it.

My engine failed,flakes all over and in oil filter,and oil drain pan.I would not run engine anymore.Hopefully oil chain is the culprit,or timing chain.Wearing against timing cover.

rebuilt m104 at ebay.de $3400 euros

one more thing.I live in the country,so I can look and dump my oil without fear around my home where i don't want weeds,or grass.thats how I can look for metal flakes.