Here's a breakdown:
* Blow-by: This is the most significant factor. Blow-by is the combustion pressure that escapes past the piston rings into the crankcase. This pressure pushes oil up past the rings and into the crankcase. Higher mileage engines with worn piston rings or cylinders experience significantly more blow-by.
* PCV System Malfunction: The PCV system's job is to vent these crankcase gases, preventing excessive pressure buildup. If any part of this system is faulty, it can lead to oil accumulating in the breather box:
* Clogged PCV valve: This is the most common culprit. The valve restricts the flow of crankcase gases, leading to pressure buildup and forcing oil into the breather system.
* Clogged or restricted hoses: The hoses that connect the PCV valve to the intake manifold or other components can become clogged with oil and sludge, restricting airflow.
* Failed breather filter: Some systems incorporate a filter to keep larger particles from entering the intake. A clogged filter can impede the system's function.
* Vacuum leaks: A leak in the vacuum lines connected to the PCV system can disrupt the negative pressure needed to effectively remove crankcase gases.
* Worn or damaged seals: Leaks in the valve cover gasket or other seals can allow oil to escape into the breather system.
* Engine condition: Generally, higher mileage engines will have more blow-by due to wear, resulting in more oil in the breather box.
* Oil level: An excessively high oil level can contribute to oil being forced into the breather system due to increased crankcase pressure.
In summary: To diagnose the problem on your 1989 Honda 2.0L, you should first check the PCV valve for proper operation (it should have some resistance when moved), inspect all hoses for clogs or cracks, and check the valve cover gasket for leaks. If these are all in good condition, consider the possibility of worn piston rings or excessive blow-by (requiring a more major engine repair). Also verify correct oil level.
