i changed my air cleaner today and noticed a milky substance in my air cleaner box,its coming from the hose that's attached to my pcv,what causes this,by the way i am a newbie and i hope i have posted in right area but i cant find the answer anywhere...please reply if you know what causes this
2000 c230 kompressor

 

check you oil. if it's milky coukld indicate a blown head gasket.

 

You are getting moisture build up in the block. Some moisture is always happening, but if your Ventalation system gets plugged or broken, that can let the moisture build up and give you the slimmy white mess. Hope that it isn't anything major like a head or gasket.
I would start by checking your PCV valve, it is quick easy and cheap to fix. Good luck

 

Good advice. In earler model cars it was loss of vacuum to the crankcase resulting in moisture build up. Same can happen in new ones but hose, valves etc must be looked at also.

 

How does the underside of your oil cap look? The milky brown water/oil mixture can show up there too.