[DBnR]

This is probably the millionth "strange noise" thread about the F30/31 but here it is anyway. I'm hoping someone here can help identify the cause of this particular noise.

It is a metal-on-metal kind of sound, or possibly a worn bearing. I haven't been able to take a video of it because it only seems to occur when driving at low speeds (below 20 km/h or so) and especially when coming to a stop. Either that or road noise drowns it out at higher speeds. It also seems to go up and down with the revs, i.e. when the car downshifts. It doesn't happen every time, either, and it doesn't seem to matter if the engine's warm or cold.

I know that's not a lot to go on but maybe these symptoms ring a bell with someone who actually knows something about this stuff.

The car is a 2013-10-04 F31 with ~187 000 km on the clock.

I'm hoping it's a bearing or something, and not the infamous timing chain. According to a mechanic it's really difficult (= expensive) to inspect the timing chain, but he said if it's going loose the noise will be obvious and "drive train malfunction" (or similar) errors will appear on the screen. In any case I did inspect the chain trough the oil filler and took a video:

Does that look ok? Seems loose to me but if it was that easy to check surely they'd do it at the dealer every time it's serviced?

[canman111]

That seems like a lot of play in the guides esp at the 00:08 second mark.

The thing with the drivetrain malfunction error is that by the time the error comes up, it may be too late.

It is possible that your mechanic has one of those cameras that can look inside through the cap and see if the guides are ok?

Maybe if you upload a video which shows the sound while the car is operating, someone else might be able to offer their insight.

[DBnR]

Sitrep. I've checked the chain twice today. First time it was about the same as in the video, second time it was tight as a drum. Both times engine warm.

I'll go to the mechanic tomorrow to have them check out the noise.

[DBnR]

Mechanic didn't hear anything alarming. He said he wouldn't have even noticed anything unless I'd said how to reproduce it. I'm fairly certain now it's ok. This car's made me paranoid

[BettyFkinCrocker]

The chain being taught or slack is not of much concern. There is a more technical explanation I'm sure someone will provide, but basically it just depends on where the engine comes to rest once shut off.

The guide definitely seems to have much more play than it should. I've tried to get a boroscope down through the oil fill hole but it's nearly impossible to see anything of value once down there. Your best/cheapest bet is to drain the oil and use a boroscope into the oil pan to look for pieces of plastic in the bottom.

[spirit3d88]

The chain has made the test with it while the engine is cold, it is normal that it is loose as it loosen.

Repeat the test with the hot engine, it should be hard and without any slack.
If you still have that hot slack, directly go to change the chain, in fact I advise you to take the car in crane to the workshop you want, since it is symptom that is about to break at any time.