What is an AOS?The engine air-oil separator (AOS) is an emissions device located on the top front corner of the left side valve cover. The separator is responsible for collecting residual gases and vapors contained inside the crankcase and funneling them back into the intake manifold where they can be burned in the combustion chamber. This reduces the overall emissions of the engine.
Common Problem:When the separator fails, it causes an increase in the overall vacuum in the engine crankcase. In the most extreme cases, the air-oil separator fails to separate the oil from the air, and oil is then sucked into the intake manifold. Oil in the intake system can cause spark plugs to misfire and destroy catalytic converters. The failure of the air-oil separator is often (but not always) accompanied by white smoke exiting the vehicle's exhaust and a generally poor running engine. You may experience a check engine light (CEL) as the oil being drawn into the intake can affect the mixture level. In addition, you may hear hissing noise from the separator when it's running. This is caused by air being sucked in past the diaphragm seal.
Solution:There is no need to spend $400+ to replace the entire valve cover. Save time and money by simply replacing the cap with diaphragm seal.
- Brand New Cap with Diaphragm Seal and Spring.
- The valve cover assembly is not included.
Engine Code: M48.00/50
Cayenne S 2003-2006 V8 4.5L
Cayenne Turbo 2003-2006 V8 4.5L
Cayenne Turbo S 2003-2006 V8 4.5L
**Will fit some 2007-2010 V8 4.8L (see second picture)
Valve Cover Part Numbers:
948-105-131-07, 948-105-131-03, 948-105-131-06,
948-105-132-07, 948-105-132-04, 948-105-132-06,