Funny metal spinning sound...

[W111AAM]

Know this may sound strange, but I will try and explain the problem as best I can.

Have noticed when I turn the engine off (and I usually blip the throttle as I kill it, no reason for it) as the engine noise ceases, there is the sound of something still spinning, only for an extra second. It sounds like a metal item, but can't see anything when I've tried looking under the bonnet.

Is it something obvious that has come loose or should I be more worried?

[boosted ls1]

Could be a loose washer. I'd check the alternator bolt and the crank pulley bolt or anything else which revolves at the front of the engine. Has the clutch been changed, release bearing perhaps.

Oh, blipping the throttle before shut down just puts fuel into the engine which won't be used properly. It may cause bore wash and premature engine wear if it dilutes your oil. Far worse in the days of carbs.

Boosted

[rfisher]

My main concern with throttle blipping is that you switch off the ecu while its doing lots of things to manage the sudden throttle increase and the electrics are pumping out lots of charge.

You can certainly pop older ecus like that - seen it lots of times with flapper 4cu units.

I always let my cars sit for a few seconds on idle before switching off.

Spinning noise may be oil or power steering pumps spinning down as these are electric motors and not engine belt driven.