Baffled. Bizarre sound after turning off ignition.

[triangularmonkey]

Help!

I'm getting to grips with an NV200 van I've recently picked up. To be fair to it, it hasn't missed a beat. However, there are a couple of niggles that have me concerned. About 7 or 8 seconds after switching off my ignition, I hear this rather odd boiiiiiing sound. The best way I can describe it is it's like what you'd expect to hear from some sort of spring gently releasing under tension. It only happens after I've done a bit of driving, just turning the van on/off doesn't do it.

I know this particular van has had the starter motor replaced in the past, as well as the alternator. This, however doesn't surprise me too much as in it's previous life it was used for catering and even had a proper oven setup in the back!

Not much more I can say, it drives pretty much as it should otherwise!

Any thoughts on this?

Edited by triangularmonkey on Tuesday 14th November 23:07

[GreenV8S]

I have no idea what sort of engine that would have, but if it has an idle control valve that may be parking itself after the engine has stopped.

[E-bmw]

Either ^^^wot 'e said or possibly the air flaps in the ventilation controls resetting.

[Mignon]

EGR valve cleaning cycle maybe.