Over time, the brass orifice can erode and enlarge. This reduces the velocity of the oil spray, meaning the spinner doesn't spin fast enough to separate oil. Simultaneously, the larger hole dumps more oil into the housing than the drain can handle, causing it to overflow out of the breather. Excessive Blow-by (Engine Wear)
The MaxxForce 13 engine, manufactured by Navistar, is well-known for its complex emissions systems, and the is a frequent source of trouble. When this system fails, it often leads to excessive oil being expelled through the road draft (blow-by) tube. Common Crankcase Breather Problems Failing Centrifugal Separator (Squirrel Cage) maxxforce 13 crankcase breather problems
While the breather itself can fail, it is often blamed for problems actually caused by "blow-by"—combustion gases leaking past worn piston rings or cracked pistons. Over time, the brass orifice can erode and enlarge