The PCV (Positive Crankcase Ventilation) system is designed to prevent emissions by drawing crankcase vapors. It operates by pulling fresh air from the air cleaner through the crankcase where it mixes with blow-by gases and then drawn through a PCV valve into the intake manifold. This consists of two hoses, one running from the air intake duct to the crankcase and another one from the crankcase to the intake manifold. The PCV valve is found in the valve cover while it connects the PCV hose to the intake manifold. The flow of high vacuum restricts that of PCV valve during idling so as to maintain its good quality. In case of abnormal operating conditions, excess gases will travel back via crankcase vent tube into air cleaner. Although no routine inspection interval is set for these valves or hoses, sludge build-up can decrease their efficiency over time. Leaking seals are caused due to clogged PCV systems. It is recommended that at oil, air filter, spark plug changes inspecting and cleaning should be done on all pcv hoses Replacement involves removal of pcv fresh air inlet hose, pcv crankcase ventilation hose and pcv valve off respectively; examine-and-change any cracked or deteriorated hoses; clean out pcv valve using solvent and compressed air or replace if residue cannot be removed; re-install as necessary.