blakemcelroy2000

Hey all. Have an 02 Targa that has excessive oil consumption. After doing some research, I investigated AOS failure. Removed the oil cap while running and encountered a loud whooshing sound and rise in idle. Is this pretty concrete evidence of an AOS failure? Just want to make sure before I go digging into the engine to replace it. I attached a video of the oil cap being removed while running. Thanks!

wdb

No video. Too few posts perhaps?

mtnroads

Any white smoke upon starting or accelerating?

DBJoe996

Search for checking the health of your AOS with a manometer. Pretty straightforward.

blakemcelroy2000

The oil cap made a very loud “sucking” sound when removed, as well as a squeaking air sound when removing. I replaced the AOS and spark plugs. Plugs were heavily fouled and intake manifold had a ton of oil in it. Despite replacing it, the oil cap still makes a air rushing sound and has a slight bit of suction when removed. Im fairly certain I replaced the AOS right, and wouldn’t a vac leak/loose hose cause less suction on the crank case anyways? Just wondering what could cause this.

mtnroads

As stated above, a manometer is a foolproof tool to check AOS function (and engine health). You'll need a 2nd oil fill cap to modify and the test is simple. Search posts by Porschetech3.

GC996

An example.

chris8382

For about $3 you could have this to do the exact same thing.

Porschetech3

OP the manometer test is the only way to positively verify function of the AOS....period..

The "slack tube" tester shown above is good only to verify a "good functioning" AOS... ( but I have always liked it !!...It shows the user has a good basic understanding of scientific methods and Physics of Automotive functions,,,BUT if testing a failing AOS, you would need a much much larger/taller slack tube..)

.Normal readings are 4-6 inches of water for factory AOS, 3-5 inches of water for UAOS, but " failing AOS's" can be as high as 25 or 50 inH20 or even on a completely blown AOS 400 inH20 ( 29 Inhg)!!! So you would need a slack tube 400 inches high ( 33.4 ft tall) to insure accurate readings and not to suck water into the intake...

And if testing the blow-by for engine health, a digital manometer with a scale of up to 50 inH20 ( 2 PSI) is required...There are some available for about $40 bucks that work very well..I use one exactly like this.....

mtnroads

Blake. You heard it directly from Da Man. Do yourself a favor and listen.