Inside your engine there are high pressure oil passages that deliver lubricating oil to the moving parts of the engine.
There are also return passages, or low pressure passages, that the oil flows through to return to the engine bottom pan or reservoir.
During engine operation, some pressure builds-up in the low-pressure engine oil passages. This pressure build-up is normal, but must be relieved.
The PCV system is designed to relieve this pressure build-up.
However, the PCV system will get clogged or sludged-up over time and not be able to perform its job. This sludge and varnish are naturally caused by oil and gasoline (hydrocarbons) in a hot engine.
When the PCV system becomes clogged, pressure builds and oil is forced out and begins to leak out of any gaskets or seals that it can. Once this begins, major engine work can be required to repair all these oil leaks.
For this reason, regular maintenance of the PCV system is extremely important.
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