[gillypop]

to take the top off the separator housing you have to remove the filter housing bolts - 4 of them. If you do this you will need to fit 2 new seals/gaskets and also need a new top to the separator as the gasket for this does not come on its own. A new seal for the dipstick tube would likely need to be replaced.

I have just checked mine at 263k and it was clean as a whistle but may not be the case on every car.

It takes about 2 hours to remove and refit and a small amount of oil is lost - when vehicle is on ramps at the front.

It costs approx £37 for the seals and top cover (called a valve). It will leak as mine did hence replacing the seals.

Brendan W 'I have an idea that the crankcase pressure goes negative over 1500 rpm or something like that so at idle a bit of fumes is normal.'

Can be observed by slightly removing the dipstick so vapour can be seen then rev slowly to 1500rpm and vapour gets sucked down.