Originally posted on M3forum, re-opening the question here since I haven't resolved it.
For a few years I've had a randomized rattle noise, like something banging around under the valve cover near the chain/VANOS area. It always happens, but has no consistent frequency / not harmonic, and it exists whether engine is hot or cold (might be louder when hot, or engine is just quieter). Hard to tell if it's really changing with RPM because it becomes difficult to hear it over the engine noise. What it's NOT: a broken piece of something banging around, the upper chain guide itself (recently replaced), normal rattle (just did anti-rattle kit + S62 springs).
Here is the original video, with the sound most obvious around 21-30 seconds: https://www.youtube.com/watch?v=mY-toVFeEFQ and a video I just took this morning (engine cold, after ~2 minutes running): https://www.youtube.com/watch?v=kJ2fmWhPbBo The noise is a little more pronounced when the engine is warm, but that could just be because it's quieter at idle when it's completely warmed up, lower rpm.
Here are my thoughts on what it could be since anti-rattle and chain guide are now out of the question...
1) Failed exhaust chain tensioner. I thought these were oil pressurized and rare to fail, but saw a YouTube video that showed how even an oil-pressurized one could fail (internal check valve allows oil to be freely back out instead of maintaining good pressure). This would be easy to replace and test, though not super-cheap (even OE is $70, BMW $230) without knowing it's actually failed. Any obvious way to tell if it's failed? Only 92k miles on the car, and the sound has been there for at least 30k miles, maybe longer.
2) A couple months ago I saw a reference to an intake-side bolt that supports the intake tensioner, and has been known to vibrate loose just enough to allow for chain rattle but not enough to leak: see #10 here: https://www.realoem.com/bmw/enUS/sho...diagId=11_3005 . It's inaccessible without removing the oil filter housing and/or water pump, and from what I've looked over that seems like a big pain. The thread author described the sound he had, which sounds similar/identical to mine, and that some thread lock and re-tightening this bolt took care of it. If/when I find the thread, I'll add it here. Not entirely sure it was an S54, but noted it is somewhat common as a VANOS gremlin that isn't actually the VANOS at all.
3) Could be something completely unrelated, with the sound traveling through the head. Maybe a bearing rattle in the water pump itself, though the sound doesn't feel like it's coming from there. Maybe the bearing on another accessory.
What do you think? Anybody have this and know what it actually was or resolved it?
EDIT: I updated this with a video from this morning. I held my hand in different spots and the rattle definitely feels like it's coming from the intake side of the chain area, and not the exhaust side or water pump itself. That lends some support to #2 being the cause.
For a few years I've had a randomized rattle noise, like something banging around under the valve cover near the chain/VANOS area. It always happens, but has no consistent frequency / not harmonic, and it exists whether engine is hot or cold (might be louder when hot, or engine is just quieter). Hard to tell if it's really changing with RPM because it becomes difficult to hear it over the engine noise. What it's NOT: a broken piece of something banging around, the upper chain guide itself (recently replaced), normal rattle (just did anti-rattle kit + S62 springs).
Here is the original video, with the sound most obvious around 21-30 seconds: https://www.youtube.com/watch?v=mY-toVFeEFQ and a video I just took this morning (engine cold, after ~2 minutes running): https://www.youtube.com/watch?v=kJ2fmWhPbBo The noise is a little more pronounced when the engine is warm, but that could just be because it's quieter at idle when it's completely warmed up, lower rpm.
Here are my thoughts on what it could be since anti-rattle and chain guide are now out of the question...
1) Failed exhaust chain tensioner. I thought these were oil pressurized and rare to fail, but saw a YouTube video that showed how even an oil-pressurized one could fail (internal check valve allows oil to be freely back out instead of maintaining good pressure). This would be easy to replace and test, though not super-cheap (even OE is $70, BMW $230) without knowing it's actually failed. Any obvious way to tell if it's failed? Only 92k miles on the car, and the sound has been there for at least 30k miles, maybe longer.
2) A couple months ago I saw a reference to an intake-side bolt that supports the intake tensioner, and has been known to vibrate loose just enough to allow for chain rattle but not enough to leak: see #10 here: https://www.realoem.com/bmw/enUS/sho...diagId=11_3005 . It's inaccessible without removing the oil filter housing and/or water pump, and from what I've looked over that seems like a big pain. The thread author described the sound he had, which sounds similar/identical to mine, and that some thread lock and re-tightening this bolt took care of it. If/when I find the thread, I'll add it here. Not entirely sure it was an S54, but noted it is somewhat common as a VANOS gremlin that isn't actually the VANOS at all.
3) Could be something completely unrelated, with the sound traveling through the head. Maybe a bearing rattle in the water pump itself, though the sound doesn't feel like it's coming from there. Maybe the bearing on another accessory.
What do you think? Anybody have this and know what it actually was or resolved it?
EDIT: I updated this with a video from this morning. I held my hand in different spots and the rattle definitely feels like it's coming from the intake side of the chain area, and not the exhaust side or water pump itself. That lends some support to #2 being the cause.
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