General oil trap

[trabant]

Hi, recently bought a '53 stilo multiwagon jtd for my son. was reading how to change the air filter and saw mention of the oil trap. On looking, the whole of the bottom of the air box is covered in damp oil (not dripping). The rest of the engine is bone dry, so where is this oil coming from and what do I do to clean it off? Is there a reservoir inside which collects oil and needs cleaning out?
Thanks for any info.

 

[Davren]

The resevoir is the square box attached to the bottom of the air filter housing.
.

 

[trabant]

Thanks, but do I just leave it covered in oil or is there a way of cleaning it out? Does it mean that something is blocked, air filter for example?