Oil separator valve e39 535i bmw

V8 BMW engine 4.4L and 4.8L have a common problem in drying after burning the valve steam seals in cylinder head, witch cause internal oil leak from the valves to the top of the pistons then the oil burns throw the exhaust valves explain the smoke from the tail pipe.
the issue will continue and will get worse with time until you replace the valve steam seals, $1500-$2500 mostly in labor, a BMW mechanic most have a special tool to do the job with out removing the cylinder heads, it's time consuming.

maybe , check for correct replace

Smoke from where exactly? Under the hood? From the exhaust? You need to be more specific.

vacuum leak, o2 sensor, oil separator problem, bad spark plugs, low fuel pressure, clooged gas filter, valve cover gasket leaks....

I HATE TO TELL YOU THIS, BUT A WHITISH LIGHT BLUE SMOKE IS NOT YOUR VALVE SEALS....IT IS YOUR PISTON RINGS. IF YOU REV YOUR ENGINE, AND MAKES MORE SMOKE, IT IS DEFINITELY YOUR RINGS.

This could be two problems occuring, 1. Head Gasket leaking intermitantly (ie) Replace Head Gasket & skim head. 2. Replace the oil separation Valve or also known as Crank Case ventilation Valve.
This valve opens & closes, can be glued shut with carbon build up. Then when engine comes under load & elevated the oil from crank vent pipe can't escape but events in burning of as white smoke.

check your anarobic switch

The smoke is blue, correct?
When you changed the oil separator, did you clean out the hose that goes from the valve cover to the oil separator?
The next suspect for smoking at idle would be the intake valve seals, but that would be the first time that I ever heard of a problem there.

You must use 5w\40 or 10w\40 remember BMW recommends castrol for engine oil