The "jet plate" is a brass orifice that sprays oil onto the centrifuge to spin it.

If the bearings fail or the assembly becomes clogged with sludge, the spinner slows down, losing its ability to separate oil from air. This causes the system to flood, forcing raw oil out of the breather tube—sometimes at a rate of several gallons per day. Jet Plate Erosion

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.

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)