try to seal the connections of the hoses with fittings so that the oil vapor gets trap in the catch can and doesn'e escape... yung oil vapor condenses near the fittings and the dirt will be attracted to that kaya dudumi yung sa meh fittings...

as for the coolant, walang correlation yun, mauubos lang laman ng reservoir mo kung meh problem sa cooling system.... very seldom should the reservoir get depleted...