AOS seperator symptoms
 

AFAIK, symptom of the AOS seperator is white smoke. About 10k miles ago, I had a code (don't remember which) that indicated the AOS could have been going out. I cleared it, and haven't gotten it since nor have any white smoke, but it feels down on power. I'm preparing for a road trip, so am doing the spark plugs, oil,and filters anyway, but should I consider the AOS? I'm 86K.

Ummm.... YES!!!

Spend <$100 and have peace of mind and you're already doing maintenance work.
or
Cross your fingers and hope it doesn't fail when you've already had signs it could be on it's way out. If it fails on your road trip, you may or may not be able to find one close by to replace it, you may or may not have had room to bring tools on your trip, and if it fails catastrophically, you may ruin your engine.

I know which route I'd go.

Just test it with a Pyle Digital manometer. $30 on Amazon.See Search.

So to confirm, buy manometer, DIY oil cap for testing pressure, test, should be 5psi?

Yes exactly

Vacuum ,not pressure

5 inches of water vacuum............

Instead of replacing the AOS with a new one , is there a way of pulling it apart and refurbishing it , has anyone done this ?

Waste of time and effort, replace it.

Before I started taking long road trips I bought a new AOS and carried as a spare. My org. AOS worked fine gave me no indication of failure. I figured I had tools so if I was stranded and isolated I at least had a chance to change myself or take to a shop and have them do it with part in hand.
I finally changed the org with the new one in my garage as prev. maint.
You on the other hand have indications it's failing. It's one of those preventative maintenance items that typically gets replaced with time. Then you can carry your org. AOS as a spare. I do in case the new one is one of those ones that fails after a few thousand miles

Yes, 5" of water Vacuum is the maximum BUT-
I just fitted a new AOS and it shows 4.6" but has huge clouds of oil smoke !
Diagnosis:
I suspected the old AOS was due for replacement based on age and some white smoke after start up. The old AOS tested O.K. but replaced it anyway. The new one seemed no different in terms of white oil smoke production.
I dissected the old AOS to see if the diaphragm was sagging/torn. It was perfect .I epoxy-ed it back together to carry as an emergency spare.
Now I have huge plumes of white oil smoke and 4.6" of water vacuum on the Pyle manometer.
BTW the oil pressure at start-up is 75+ lbs on a newly rebuilt engine and the compression/leakdown is perfect and even on all 6 cyl
So is the 4.6" AOS defective/marginal ? What should a new, perfect AOS measure? Pelican say 4-7" and above 9" is a fail. They have an excellent DIY here:
"If you're still not sure, you can take a closer look at the hose that connects the air-oil separator to the intake manifold (yellow arrow, Figure 2). If the unit is failing, then there will be a significant amount of oil or residue in this tube. If the car is running rough, then removing this tube and blocking off both ends should disable the system and restore previous performance. This is not a long-term fix, but instead a short-term diagnosis step to use before you replace the air-oil separator."
http://www.pelicanparts.com/techarticles/Boxster_Tech/09-ENGINE-Air_Oil_Separator/09-ENGINE-Air_Oil_Separator.htm
http://cdn4.pelicanparts.com/techarticles/Boxster_Tech/09-ENGINE-Air_Oil_Separator/images_small/Pic2.jpg
I ask because there has been discussion of defective,new AOS units from even reputable suppliers. I bought my new (4.6") one from name begins with Auto and ends AZ******************************** Az., hmmmmm.