Toyota 12204-50030 Valve Sub-Assy, Ventilation

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The Positive Crankcase Ventilation (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. The system consists of the PCV valve and two hoses, one connecting the air filter housing to the crankcase and the other connecting the crankcase to the intake manifold. The PCV valve restricts flow during high intake manifold vacuum to maintain idle quality, but allows excessive blow-by gases to flow back into the air cleaner during abnormal operating conditions. While there is no scheduled inspection interval for the PCV valve or hoses, over time the system may become less efficient due to oil residue build-up, leading to symptoms such as leaking seals. It is recommended to inspect and clean the PCV hoses during routine maintenance tasks like oil changes, air filter replacements, and spark plug replacements. If the hoses are cracked, torn, or deteriorated, they should be replaced. The PCV valve should also be inspected and cleaned with solvent and compressed air, or replaced if residue cannot be removed. The process of removing and installing the PCV system components involves disconnecting hoses and unscrewing the PCV valve, and the condition of the hoses and valve should be carefully inspected before reinstallation.

It is recommended to inspect and clean the PCV hoses during routine maintenance tasks like oil changes, air filter replacements, and spark plug replacements.