Toyota 12204-38010 Valve Sub-Assy, Ventilation

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The Positive Crankcase Ventilation (PCV) system reduces hydrocarbon emissions by circulating fresh air through the crankcase, mixing with blow-by gases, and drawing them into the intake manifold. It consists of a PCV valve and two hoses connecting the air filter housing, crankcase, and intake manifold. The PCV valve restricts flow during high vacuum for idle quality but allows excessive gases to flow back during abnormal conditions. The system may become less efficient over time due to oil residue build-up, leading to symptoms like leaking seals. Routine maintenance tasks like oil changes, air filter replacements, and spark plug replacements should include inspecting and cleaning the PCV hoses. Cracked or deteriorated hoses should be replaced. The PCV valve should be inspected, cleaned, or replaced if residue cannot be removed. Careful inspection of the hoses and valve is necessary before reinstallation.

The PCV system is responsible for reducing hydrocarbon emissions by circulating fresh air from the air cleaner through the crankcase, where it mixes with blow-by gases, before being drawn through a PCV valve into the intake manifold.