How to test Auxiliary Air Valve

ManniB · 03-22-2013, 09:30 AM

While stripping down my '81 SC engine (930/16) for chasing oil and vacuum leaks, I wondered how I can bench test the AAV.

Thanks, Manfred

T77911S · 03-22-2013, 10:33 AM

with a hand vac pump. you have to cover one side with your hand. my pump came with big rubber fitting that i was able to use. i think it only works when pulled on one side. it was a bit tough to do.

ManniB · 03-22-2013, 09:56 PM

Thanks T77911S, I wil try that.

- Manfred

Jim Williams · 03-23-2013, 06:44 AM

You can use a Mity-Vac and a 90˚ spark plug boot per the attached photo. The vacuum has to be pulled on the connection as shown and the other connector covered until a good vacuum is showing (6"-8"). Then release the finger seal and the vacuum should remain. A very slow drop in vacuum is still a passing grade as the vacuum is being continually replenished by the engine.

There are other ways to test, but they require disconnecting and plugging the hose ends, then starting the engine and comparing the way it idles with how it idled before the plugging of the hoses. So you may as well remove it to check it and know for sure.

ManniB · 03-23-2013, 10:37 AM

Jim and T77911S,

thanks for the explanation. I did the test as per what you described and it passed. One less part to care about

- Manfred