2nd Gen R56 Cooper S Engine slight overlapping knocking sound coming from cylinder #4

About three months ago I started to noticed when getting off the freeway a slight overlapping knocking noise that I have pinpointed to the (above) cylinder next to the timing chain and or the Vanos solenoid for which I understand in on the intake side of the head. I have only heard this noise six times in about three months, if I shut off the engine and restart the engine the sound is gone except for today.

I went away after several minutes, came back and noise disappeared, I probably won't hear it for another 2-3 weeks. If the Vanos solenoid is located near that cylinder is it possible it could be the Vanos solenoid causing this sound by not making any change to the cam timing from getting off the freeway? Perhaps when I get off the freeway the Vanos gets stuck and thinks I'm still at 3000 rpms when infact I'm at idle. I'm 95% certain the overlapping noise is a cam lobe hitting something.

Feedback needed and appreciated!

Regards,
Systemlord.

 

I check my oil religiously every three gas tanks, my MCS doesn't burn through much oil like most N14's do, more like an N18. I checked my oil anyway right after the noise went away, down to the first mark on the top of the Craven dipstick. My valves weren't that bad at 47k when I had them walnut blasted. Are my lifters hydraulic and could that be my issue? Also can the lifters be replaced without removing the cams? It doesn't happen when the engine is cold, it happens after prolonged freeway driving and as soon as I come to an idle it can be heard, but doesn't happen often enough. Turning off the engine seems to clear it right up, weird!

I don't understand how turning off the engine would make much difference on a mechanical moving part. My only guess now is a sticky lifter that doesn't lift up all the way, I mean if a lifter is getting struck after the cam lobe swipes it that might explain the lobe hitting it when it's stuck compressed creating that overlapping knocking sound. If this is something that requires removal of the cams you will be the first to know about it.

Compression is, it builds up quick in all four cylinders.

#1 155
#2 153
#3 154
#4 156

 

I have own the Mini for a little over a year and never heard that sound before, today it was quieter than usual, but the other times it would turn heads if anyone was near the Mini. I expect as time goes on it will become more frequent , thank God I have 5 years left on my warranty!

This month (June) I'm planning on doing some long distance driving with the BG 44K in my tank to further clean my carbon buildup in the combustion chambers, I will drop by then to get a look at your shop for sure.