Toyota 12204-31030 Valve Sub-Assy, Ventilation

The Positive Crankcase Ventilation (PCV) system reduces hydrocarbon emissions by scavenging crankcase vapors, circulating fresh air from the air cleaner through the crankcase to mix with blow-by gases before being drawn through a PCV valve into the intake manifold. This system includes the PCV valve and two hoses: one connects the air filter housing to the crankcase, while the other connects the crankcase to the intake manifold. On V6 models, the fresh air inlet hose connects the right valve cover to the air filter housing, with the PCV valve located at the rear of the left valve cover. For four-cylinder models, the fresh air inlet hose connects the intake air connector to a pipe on the valve cover, with the PCV valve at the right rear corner. The PCV valve restricts flow to maintain idle quality when intake manifold vacuum is high, allowing excessive blow-by gases to flow back into the air cleaner under abnormal conditions. There is no scheduled inspection interval for the PCV valve or hoses, but efficiency may decline over time due to sludge buildup, leading to symptoms like leaking seals. During oil changes or other maintenance, it's advisable to inspect and clean the PCV hoses, replacing any that are cracked or deteriorated. For V6 models, detach the PCV hose from the valve and unscrew the valve from the left valve cover, inspecting and cleaning or replacing it as necessary. For four-cylinder models, detach the PCV hose and unscrew the valve from the valve cover, similarly inspecting and addressing any issues with the hoses and valve. Installation follows the reverse order of removal.

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.