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An inexpensive way to test for a bad AOS

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An inexpensive way to test for a bad AOS

There are a lot of indicators for a bad Air Oil Separator. 1. Excessive white smoke out the tail pipes. 2. Excessive vacuum on the oil filler cap, making it very difficult to remove, and once it is off the engine idle will become very rough and might stall. 3. Excessive oil in the tube leading from the AOS to the plenum behind the throttle body, and even excessive oil in the intake plenum. (a light film of oil is considered normal) 4. High pitched screeching noise from the AOS unit itself.


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I recently used your DIY and created my own AOS tester. Here is a shot of an adapter attached to my oil cap.


Here are two photos of the air tube with one end attached to the oil cap and the other to the gauge.



I marked the start and then the finish after opening the valve to the oil cap.



Here s a short movie clip of activating the valve by the oil cap.

Edited by kbrandsma
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