Lexus 12204-20040 Valve Sub-Assy, Ventilation

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The Positive Crankcase Ventilation (PCV) system reduces hydrocarbon emissions by directing blow-by gases and crankcase vapors into the intake manifold. Fresh air from the air filter housing mixes with these gases in the crankcase before exiting through the PCV valve. During idle and part-throttle conditions, blow-by gases flow through the PCV valve into the intake manifold, while fresh air is drawn into the crankcase. Over time, sludge buildup may reduce the system's efficiency and cause leaks. Regular checks and possible replacements of the PCV valve and hoses during routine maintenance are recommended.

The PCV valve restricts the flow when the intake manifold vacuum is high to maintain idle quality.

The PCV valve and hose is located in the valve cover.

When purchasing a replacement PCV valve, make sure it's for your particular vehicle and engine size. Compare the old valve with the new one to ensure they're the same.

Checking and potentially replacing PCV components, such as the PCV valve and hoses, is recommended during routine maintenance tasks like oil filter changes, air filter replacements, fuel filter replacements, or spark plug changes. This helps ensure the continued effectiveness of the PCV system.

With the engine idling at normal operating temperature, place your finger over the valve opening. If there's no vacuum at the valve, check for a plugged hose or valve.