Combustion blow-by gases inevitably enter the crankcase past the piston rings, and the crankcase ventilation valve — sometimes called the PCV valve — is what controls their controlled return to the inlet tract rather than allowing pressure to build and force oil seals outwards. On modern direct-injection petrol engines and common-rail diesels, the valve is typically an electronically regulated or pressure-differential component rather than the simple one-way reed valve of older designs. When it fails in the open position, oil mist is drawn into the inlet in excessive quantity, coating the intercooler, fouling the throttle body and EGR valve, and in severe cases causing uncontrolled engine run-on from oil combustion. When it fails closed, crankcase pressure rises until the path of least resistance — usually an aged crankshaft seal or dipstick tube — begins weeping oil. BMW engines are disproportionately represented in the fitment data owing to their notorious plastic valve-and-separator assemblies that harden and crack with age; Volkswagen Group engines with the EA888 family are similarly prone. VAICO and BOGAP are among the specialist suppliers offering replacements for these applications, with A.Z. Meisterteile covering additional German premium applications.
Crankcase ventilation valves are engine-family specific, and even within the same model line the valve design changed significantly across production years. Use the make, model, engine code, and year on this page to display the TecDoc OE references that match your exact engine build. For BMW and Volkswagen Group engines in particular, there were multiple revised part numbers issued over the production run as original plastic components proved insufficiently durable — the most current OE reference is the correct one to fit.
OEM valves are calibrated to the specific inlet vacuum and blow-by pressure characteristics of the engine they serve. Quality aftermarket replacements from VAICO or BOGAP are engineered to the same flow and pressure specifications. Very cheap alternatives may use the same external shape but different internal membrane or valve geometry, which alters the pressure regulation behaviour — leading either to oil consumption from over-ventilation or crankcase pressurisation from under-ventilation, neither of which triggers an obvious warning light until secondary damage has accumulated.
Yes, and this is one of the more commonly misdiagnosed sources of oil loss on European premium vehicles. When the valve fails in the closed position, crankcase pressure builds up and seeks the weakest seal in the engine — typically the crankshaft rear seal, the rocker cover gasket, or the dipstick tube. What looks like a seal failure is often actually a pressure problem caused by the blocked ventilation valve. Replacing the seals without addressing the blocked valve results in the new seals beginning to weep again within a few thousand miles.
A valve stuck open typically causes blue-grey smoke from the exhaust at light throttle as excessive oil mist enters the combustion, an oily film building up on the inside of the air filter housing or intercooler pipes, and fouling of the throttle body. A valve stuck closed causes rising crankcase pressure, oil seepage from gaskets and seals, and sometimes a whistling or hissing sound from a pressurised dipstick tube. On vehicles with a check engine light, a blocked ventilation valve can set codes related to the MAP sensor or intake system vacuum if it affects boost control.
Showing 100 of 1,303 Crankcase ventilation valve OE numbers. Enter the OE on the main OE search to jump to any reference.
