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Discussion Starter #1
Seems to only happen when car is heated up to operating temp, wondering whether it's likely related to a vanos issue, or chain tensioner, or can anyone suggest any other possibilities?

I fully intend to take it to a specialist to have it looked at, however I always like to do a bit of background work in advance to assist in a possible advance prognosis. Thanks.
 

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Discussion Starter #3
Same, I changed the vanos solenoid seals not long ago so that should be ok.
Someone suggested that one of the pistons might be sticking, I did clean them when I did the seals but I guess you never can tell unless you take it apart again and test it. I work away a lot, so I haven't had much time to mess with it yet.
 

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I'm having a similar issue, i'm thinking its timing chain tensioner, thats at least where i'm going to start
 

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As you say a VANOS piston rapping against the front cover (try a mechanics stethoscope on the cover to confirm).

Or the main chain tensioner sticking (easy to fix).

Or a valve lifter (usually loud cold as well, though).

Or rod bearings. Try revving slowly up to 2500-3000 rpm. If the rapping gets much louder around 2500, it's likely rod bearings).
 

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I've got this too, bank 1 also. (Passenger side US car). Intermittent, only at idle when warm. Goes away with very slight increase of rpm from idle. Also thinking was chain tensioner or vanos, but also been working too much to have time to delve into it, and had other "fires" on all the vehicles to put out to keep a functional car running for transport. Also makes a similar more rattly noise on start up (vanos?) that goes away in a second or 2.

Pretty sure it's not lifters and have driven an S62 with rod knock. I found that noise was most pronounced at around 2500rpm in second gear with light-moderate acceleration, this is not that.
 
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