What is the Crankcase Vent Filter?
The most common application for the crankcase vent filter is on high performance engines such as race cars, though it is extensively used on older models of vehicles as well. Inside the engine, small amounts of combustion gases push by the piston in the cylinder and enter the crankcase, or the bottom end of the engine. These gases generate a positive pressure inside the crankcase, which requires ventilation. Positive crankcase pressure robs the engine of power as the pistons have to fight against that pressure when performing each down stroke.
A breather tube is fixed at the top of the crankcase in the engine block that releases the positive pressure into the environment or into the intake to cleanly burn them before they enter the atmosphere. The breather tube contains a port or elbow at some point along its route where the crankcase vent filter is fixed. The crankcase vent filter lets excess pressure to push out into the environment without taking oil particles or other messy contaminants with the gases. It also stops any debris or dirt from going into the crankcase if there is a situation where negative pressure occurs, such as engine cooldown. If the crankcase vent filter is plugged, the excess positive pressure inside the crankcase can blow out engine oil seals. If the crankcase vent filter isn’t in place, dirt can enter the crankcase and plug oil galleries or contaminate the oil, which can cause lasting engine damage.
Facts to Note:
The crankcase vent filter operates opposite to how other filters operate. Its main function is to stop contaminants in the engine from going into the atmosphere, while most other filters prevent contaminants from entering the engine.
How to Fix:
The crankcase vent filter is confirmed that it needs to be changed. The air filter housing is then opened.
The faulty crankcase vent filter is removed by disconnecting the vent hose and removing the clip.
The new crankcase vent filter is fixed and secured with a clip. The vent hose is then connected.
The air cleaner housing is closed. The crankcase vent filter is then tested for operation.
The vehicle is road tested to ensure proper operation of the crankcase vent filter.
The crankcase vent filter will suddenly become plugged with oil that is carried by the exiting vapor. It should be inspected whenever the engine air filter is swapped, and should be changed at least as often as the spark plugs. If you experience signs that may be associated to the crankcase vent filter, have one of your expert technicians diagnose and replace the vent filter.
Common signs indicate you may need to change the Crankcase Vent Filter:
Oil on the engine
Plugged filter causing engine seals to leak
Decrease in engine performance
Importance of this service:
When the crankcase vent filter is plugged, engine oil will leak when seals are pushed out. If the vent filter is missing or broken, contaminants can enter the crankcase. If the vent filter is not in place, an oily mess can occur under your hood. It is prudent to replace the crankcase vent filter as soon as needed.