should a vanos rattle

[sex instructor]

had my car in for an inspection 2 today with a respected indy and he says it should rattle on start up and switch off and a slight rattle on revving i always though it should be quiet

[blackspider]

The majority do on start up,the reason they do is it needs to build up oil pressure-the noise you can here is the pistons inside the vanos chattering.This tends to last for a second or two.M3 and M3 evo are the loudest and most prone to failure.
They are meant to retain a certain amount of the oil for start up-the M5 e39 used to suffer badly with this and eventually it was over come by fitting a non return valve in the oil line.

It should be quite when you turn the engine off as they are still at running pressure.If it is chattering then it may suggest wear.

What M is it?

[sex instructor]

m3 evo he said he would be more worried if it was quiet when turning off

[blackspider]

It depends on how loud the chatter is.When they start to fail its a really harsh chatter which can be heard with the bonnet shut.The ones that I have replaced sound like marbels in a can-very loud.The Evo is the loudest at chattering but it doesnt always mean it is or has failed.

If you havent got any other symptons other than a chatter-ie flat spots,poor starting,hunting etc then it suggests all is well.
The way to prove its ok is to put it a test module but that is done a stealer-this operates the vanos to all limits and loads and most pass this test.