Identifying Air-Oil Separator Failure in Your Porsche

Is there blue smoke coming from your Porsche’s exhaust? Do you notice any knocking or whistling from the engine compartment? Is your vehicle using noticeably more oil than it should? If you answered yes to any of these questions, there may be an issue with your air-oil separator (AOS).

Porsches are prized for their high performance, excellent speed, and overall reliability, but like any automobile, they have parts that can and do wear out over time. One part that is known to have a higher-than-average failure rate, particularly in Boxster, Cayman and 911 models, is the air-oil separator. The air-oil separator, or AOS, is a component of your Porsche’s crankcase ventilation system, responsible for filtering oil from the air inside the engine before it returns to the intake system. This process keeps oil inside the engine and helps limit emissions. When the AOS fails, oil is drawn into the intake manifold, which can damage the engine and lead to expensive repairs.

Here are some signs to help you spot a failing AOS, and what you can do to fix it.

Common Signs of Air-Oil Separator Failure

• Overconsumption of Oil: If your car is using more oil than it used to, that can mean the AOS is damaged. Since the separator is supposed to prevent oil from entering the intake, a malfunction results in a high loss of oil that can show as consistently low oil levels. Having oil where it doesn’t belong is bad, but so is not having oil where it’s needed, and the two combined can mean severe damage to your engine.
• Rough Idle or Poor Engine Performance: A faulty air-oil separator can introduce excess oil vapor into the engine, disturbing the normal air-fuel mixture. This can result in rough idling, misfires, and other forms of poor performance. If your Porsche has a rough idle, hesitates during acceleration, or feels sluggish, it may be the fault of a damaged AOS and should be scanned as soon as possible.
• Oil in the Intake System: A defective AOS may let oil into the intake manifold, throttle body, and air filter. If oil is present in any of these places, then there is an obvious separator malfunction. Further complications like blockage of air passages and damage to sensors are likely if the issue isn’t fixed as soon as possible.
• Check Engine Light (CEL) is On: Air-oil separator failure may cause vacuum leaks or incorrect air-fuel ratios to trigger the CEL. Some common symptoms of AOS failure can be detected by a diagnostic scan, including issues with lean fuel mixtures and misfires. Although problems with other symptoms can cause these issues, a bad AOS is more frequently the cause in Porsches.
• Whistling Noises from the Engine: Another sign of AOS failure is a whistling noise from within the engine compartment. This happens because a failed separator can cause high pressure to build up in the crankcase compared to a relatively low pressure outside the crankcase. This difference in pressure forces air through seals and gaskets.

What to Do If Your Porsche’s Air-Oil Separator Fails

• Check for Symptoms: If your Porsche is smoking excessively from the exhaust, using up oil quickly, or running poorly overall, you should take it in for an inspection immediately. Continuing to run the car with a faulty AOS can result in severe damage to the engine.
• Replace the Air-Oil Separator: The most effective fix for a problematic AOS is to replace the component. Different Porsche models have their own air-oil separators, so always make sure to choose the right one for your car.
• Consult a Professional: A mechanic can perform a vacuum test and check the intake system for the presence of oil, which may indicate that the AOS is the problem. An expert Porsche technician will also look for diagnostic codes from an engine check and physically inspect the hoses and seals.

Visit Our Porsche Professional At Bluewater Performance

As a company that specializes in Porsche repairs and maintenance, Bluewater Performance also offers a full range of services, including air-oil separator replacement. We pride ourselves in offering our Denver, CO clients with the best services by using only the best parts and tools in diagnosing your Porsche. Contact us today for an appointment!