I took it past a trusted mechanic this morning. He and another guy spent about 20 mins with it up on the hoist with a stethoscope trying to diagnose, but were pretty baffled. Hard to isolate the noise.

He feels it isn't a bottom end knock as they're normally present from the moment the engine starts, where as mine comes on about 20sec after starting (cold or hot). Obviously there are no certainties without opening the motor, but he did feel that it was a top end issue, perhaps a sticking lifter that was perhaps echoing down. His advise at this stage is to drop the oil, inspect for metal, then put in an lifter additive (not his preference, but at this stage he said anything is worth a go).

I'd already planned to do an oil and filter change this weekend, so I guess we'll wait and see.

Has anyone done a hardcore engine flush before? Something like Liqui Moly Engine Detox? I don't generally like putting in additives as they're often bandaid fixes, and an all out engine flush could dislodge some nasty stuff and move it into places it doesn't want to be........but any feedback is welcome.

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2005 3.0d Sport - Sapphire Black
Engine : Bluefin Superchip Tune,
Wheels & Sus: Style 168s (10.5s all round), H&R RDA Spacers, Bilstein B12, Eibach 40mm drop, Whiteline RSB
Exterior: Le Mans flares, 4.6is kit F&R
Interior: Dynavin N6, Blackvue DR650 dash cams

My Build Thread: http://www.xoutpost.com/bmw-sav-foru...run-sheet.html