What is the purpose of the Positive Crankcase Ventilation (PCV) system,PCV Hose and PCV Valve and how to replace on Subaru Legacy?

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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, where they are mixed with intake air before entering the combustion chambers where they mix with the air/fuel mixture that gets used during combustion. It does so by taking fresh air from the housing of an air filter and then routing it through a group of tubes into the crankcase where it mixes up with blow-by gases before being extracted out of this area through PCV valve via intake vacuum, which finally directs them into the intake manifold. The throttle body is connected to PCV valve and there is a ventilation hose, leading from it to a vented chamber inside the engine, such that when you lift off or close your throttle valves, vacuum created in your intake manifold pulls fresh air through both these hoses into your engine. However, at full throttle opening, there is usually not enough vacuum generated within your engine's intake manifold to be able to suck any additional atmospheric pressure inside its crankcase neither can it draw out any leftover blowby gases or even vapors from this crankcase. Instead, other conduits allow more than sufficient amounts of these two substances to escape from the engine block while ending up in either its induction pathway like cold-air pipe or even in an open-element type of air cleaner that could be contained within one's vehicle's hood; whereby all this happens simultaneously as we have mentioned earlier. It is important for one to regularly check their PCV system for clogs or damage because if this passage gets obstructed then leaking seals start happening among other things. There are easy ways of checking fresh air inlet tubes for cracks and wear; replace any malfunctioning ones found here after disconnection. A second component making up part of an emission control system fitted onto most vehicles' engines is known as your "crankcase ventilation" hose meaning that this would also need inspection as well. PCV valve, which is on a crankcase's right rear corner, can be unscrewed and substituted as necessary. One must always maintain their car's PCV system regularly so that it functions optimally as well as emits less amounts of harmful substances into the atmosphere; this guarantees effective performance since all wastes produced tend to minimize when dealt with immediately.

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