New AOS failing?

[Jake Raby]

We are seeing more and more bad genuine AOS units these days. Perform a manometer test to really judge the AOS health. We test every new unit just after install and find that 1 out of every 6 has an issue of some sort.

[paulofto]

Originally Posted by Jake Raby

We are seeing more and more bad genuine AOS units these days. Perform a manometer test to really judge the AOS health. We test every new unit just after install and find that 1 out of every 6 has an issue of some sort.

Not good news. So what would you recommend? Is there an after market unit or a knock off available that does a better job? Or should we go the route Stelan went and build our own?

Or, can a unit be checked BEFORE it goes in?

[jdraupp]

Originally Posted by paulofto

Not good news. So what would you recommend? Is there an after market unit or a knock off available that does a better job? Or should we go the route Stelan went and build our own?

Or, can a unit be checked BEFORE it goes in?

The only other one I know of is the racing aos that's designed to withstand track days but it's around 1000 bucks.

If I'm recalling correctly, Jake engineered one but as I recall him saying it was too expensive to produce and buy.

[Gelbster]

Jake's info is very useful. a 1 in 6 failure rate on OEM AOS is appalling. Thanks for sharing Jake.
The unit mentined by Jdraup above is the "Motorsports" AOS.It is MUCH larger so it does not fit without mods & problems.
http://forums.pelicanparts.com/boxster-cayman-forum/606549-motorsports-air-oil-separator.html
Stelan's mod not only fixes the problem:
1. it is easy to replace if the pcv fails using a widely available inexpensive part.
2. it fixes/eliminates other fragile components in the system.
3. it is inexpensive compared to any other so-called solution.

Problem: it would fail smog visual inspection.

But on a Boxster, I doubt a Smog Tech would ever be able to see the mod in his visual exam.
I am looking forward to seeing Stelan's DIY write up and photos. I'll provide some links to the main components that I find.
For those who are worried that this is a weird hack, it is quite familiar to those of us who have tinkered with supercharged or turbo engines. There are no moving parts ,fewer total number of parts, fragile parts eliminated, generic parts used, more space created to work on the engine.
If you are worried about sludge accumulating on the stainless steel 'pot scrubbers' - it is easy to remove the canister and extract the s/s pads to rinse them in gasoline.
If you are worried about Smog test results/pollution, my experience with Jaguar s/c engines using similar diy devices is that the results are improved - probably because of the improved passive 'scrubbing' by the pads ?
Thanks for sharing this fix Steve.

[JFP in PA]

Originally Posted by paulofto

Not good news. So what would you recommend? Is there an after market unit or a knock off available that does a better job? Or should we go the route Stelan went and build our own?

Or, can a unit be checked BEFORE it goes in?

Not to my knowledge, but this is why we also test everyone that comes into the shop with a digital manometer, as well as every new one we install. We have also noted failures of newly installed units, but perhaps not as many a Jake has, but that could simply be the luck of the draw. Some of these things seem to live forever, others have the life expectancy of a May fly.

[Gelbster]

ALM001 -a.k.a Andrew sent me a failed AOS so I could try a repair technique I had theorized about using a Teflon diaphragm instead of the OEM material.
I dissected the valve/diaphragm using a Dremel tool. Yes, there is the obvious tear in the diaphragm but the cause may not be inadequate material quality ? The center of the diaphragm had a 'piston' that opens and closes ports with vacume/spring pressure.The piston was jammed in the bore.This blocked the ports.The spring was perfect but was incapable of pushing the piston in the bore to open the ports.
My conclusions are
1. it would be impractical to attempt to glue in a replacement diaphragm
2. it would not solve the jammed piston problem?
3. the best alternative to an oem AOS would be Stelan's (Steve) system.
Steve explained his improved AOS very well.See below. All we need now is for others to encourage Steve to give us the details in a DIY write-up.
"Here is how I fixed, like I said I will post pics eventually but I hope this does for now

I purchased a 1 quart stainless steel (aluminum will work too) cylindrical container with a screw on cap, the cap is the size of the entire opening, I welded 3 bungs at the bottom, at the same level, meaning at the bottom, two were 1" and one was 1/4 npt
Then I took a long 1" rubber hose and ran it from one bung of the container to the vent fitting on the drivers side of the engine and clamped, I also capped the check valve opening on this fitting.
Then a very short section of the hose from the second bung from the container and installed right over the original AOS location tube coming straight up from the block (where the accordion rubber boot connected originally).

Then a small 1/4" hose to a piece of tubing that I machined a couple of slots and installed orings and inserted into the small block opening where the small fitting used to be.

placed a stainless steel mesh on the inside bottom of the container, then filled with washed and rinsed stainless steel wool, (use the heavy duty one not the fine one that may break and get pieces of ss into the block) I tested the one I use by pulling and compressing and basically distressing it and it did not flake or break).
then another stainless steel mesh disk on top of the ss wool.
Then I drilled the cap and installed a grommet to accept a standard vw PCV valve (which is exactly a diaphragm like the one we are replacing) one from a vr6 I believe is the one I purchased for about 16 or 20 bucks but you can use from a volvo or a vw1.8t. and connected another section of 1" rubber hose from the pcv valve to the throttle body to replace the j-tube and clamps

After 3k mile trip the inside of the intake, throttle body, etc are dry as dry can be.

This are the benefits I see.

- Next time the diaphragm fails it will cost me a few bucks and it takes 2 minutes to change.
- the thousands of swirls that the steel wool provides to condensate and separate the oil from the vapor are way more efficient than a single empty swirl cavity in the OEM AOS

-I can open the can anytime to see what's going on inside every oil change, last time I checked after that long trip only the bottom part of the ss wool was a little oily.

-I actually got rid of the remote oil fill in the trunk and long dipstick at the same time as they were bad as well, I installed a freeze plug on the top and now I fill my oil thru this new AOS can. and I fabricated a new short dipstick that is marked every quart exactly. I got rid of many potential vacuum and oil leaks all at the same time.
(one disavantage of this is that I have to open the engine cover if I want to chek my oil level but the good thing is that my dash gauge is calibrated accurately)

- My new redneck AOS actually pulls vapor thru all 3 openings in the engine and it drains oil thru ALL 3 of them too so the container will never fill up. (versus the OEM AOS with it's small drain).

- By replacing all plastic tubes with rubber hoses the crack-prone and vacuum leaks are virtually eliminated (and by instaling clamps and not o-ring clips as OEM too)

-The main function of the diaphragm (glorified PCV) is to let vapor go from the inside of the engine block back into the intake where it will be burned. but has to do this at a certain pace and under certain conditions:

1 - when idle (high intake vacuum) the diaphragm closes so the engine does not sees this a vacuum leak. (that's why many bad AOS's give you a CEL and rough idle.)

2- under load (medium intake vacuum) open and closing to let most of the vapors go thru and burn.

3 - Cruising (no intake vacuum) completely open so all fumes get burned.

Another way of doing this is to take the hose from the top of the container (without pcv valve) and instead of running to the throttle body, run it to your air filter box, then you are completely bypassing the problem and you will never need a new diaphragm anymore (you will need to plug shut the throttle body opening)

Regardless you need tu pull fumes from the engine block to keep your oil healty and to avoid pressure build up tha causes oil leaks at the IMS, MBS, spark plug tubes, etc."