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Old 01-19-2016, 10:48 PM   #1
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New AOS failing?

Bought a new AOS and bellows from a dealer a few months ago. I needed the part quickly as my original bellows has a gaping hole in it (and decided why not do the whole AOS). I forgot the exact part number that I got from the dealer but I checked it at the time and it was the newest revision for MY99. I installed the new AOS and all was well.

After checking the J tube over the weekend, it has oil in it, I would say just as much as when I was using my previous AOS, which didn't have any symptoms of failing besides a bit of oil in the J tube.

Is there any reason a new AOS would do this? I expected a bone dry J tube.

Thanks

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Old 01-20-2016, 11:04 AM   #2
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I am guesting that the 'J-tube' you mention is the tube that connects the TB to the AOS.
I would think that even a healthy AOS is going to be moving some oil (vapor) into the TB so the 'J-tube' would always have some oil in it. Just guessing here

All the problems I here about here with new AOS's not being very dependable has kept me from replacing mine. I bought a new AOS over a year ago, still sitting in the box.
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Old 01-20-2016, 11:22 AM   #3
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I installed a new one, after an AOS failure, from Pelican a couple years ago and no problems.

You do have to be careful with the bellows to ensure you get it installed properly as its quite tight in there and hard to see.

I used a bore scope to verify everything was fitted properly after the install.
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Old 01-20-2016, 01:09 PM   #4
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I had a few follow up examinations with the new bellows and it is indeed finally sitting perfectly with no leaks to be seen.

All other connections are free of oil seepage and the like.

I guess my question is how likely is it that my AOS is 'bad' or that there is some other symptom 'killing' my previous and new AOS? Also, is it indeed normal to have oil in the tube from the AOS to the TB (J tube on 97-99 years)?
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Old 01-20-2016, 01:43 PM   #5
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Can a new AOS be bad? Decidedly yes, we have seen it happen more than once.

The best method to test an AOS, old or new, is with a digital manometer connected to the oil fill cap; if you see vacuum in excess of 5 -6 inches of water (not mercury), the AOS is bad.
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Old 01-20-2016, 05:10 PM   #6
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Some are bad even new, but all are bad by design, I made a custom one and got rid of the problem for good
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Old 01-20-2016, 07:27 PM   #7
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Is any amount of oil in the j tube acceptable with a new AOS?
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Old 01-21-2016, 01:59 AM   #8
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Quote:
Originally Posted by epapp View Post
Is any amount of oil in the j tube acceptable with a new AOS?
One purpose of the AOS is to pull a low vacuum (5 inches of water) on the engine case. In the process of doing that, it is going to pull some oil vapor into the tube.

Again, check your vacuum level, if it is correct, nothing is wrong with the AOS.
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Old 01-21-2016, 07:01 AM   #9
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I am currently running low on my manometer count, but I understand the idea and why there might be vapor in the tube/ oil to be found. I just thought a healthy air oil separator would separate the oil from the air???
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Old 01-21-2016, 07:38 AM   #10
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Originally Posted by epapp View Post
I am currently running low on my manometer count, but I understand the idea and why there might be vapor in the tube/ oil to be found. I just thought a healthy air oil separator would separate the oil from the air???
It does, but not every last molecule, and some ends up in the tube.

But if you still think you have a problem AOS, test it, that's exactly what shops do.
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Old 01-21-2016, 07:50 AM   #11
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Originally Posted by stelan View Post
Some are bad even new, but all are bad by design, I made a custom one and got rid of the problem for good
Stelan,
Your custom design is very interesting because the AOS failure is a frequent issue here.
Can you share your design idea with us?
One other member used some BMW parts, some have modified 'catch cans' with or w/o the AOS. I have a project to replace the Buna diaphragm with a Viton piece. But nobody(yet) has an effective improvement for the AOS.
Yes, the "Motorsports" version is better but it is larger and more difficult/impossible to fit for the average DIY guy.
So tell us about your creation please?
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Old 01-21-2016, 04:46 PM   #12
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Quote:
Originally Posted by Gelbster View Post
Stelan,
Your custom design is very interesting because the AOS failure is a frequent issue here.
Can you share your design idea with us?
One other member used some BMW parts, some have modified 'catch cans' with or w/o the AOS. I have a project to replace the Buna diaphragm with a Viton piece. But nobody(yet) has an effective improvement for the AOS.
Yes, the "Motorsports" version is better but it is larger and more difficult/impossible to fit for the average DIY guy.
So tell us about your creation please?

I travel almost half of the year supervising companies overseas so I will describe it with words until I get back to take some pictures as I'm about 3k miles from my car at the moment.

First I removed and dissected the original AOS which was not bad but it was getting my intake and idle control valve oily, this is what I found to be wrong in my opinion:

a) The actual bottom of the AOS is just an empty half a swirl cavity, this is the part that separates the oil, not the diaphragm. and it does it halfway as it is just a half a swirl.

b) there are 2 openings at the bottom of the AOS, one is the inlet in which the accordion large hose attaches to and small oil return to drain oil back into the block
notice that the small one is too small to actually drain oil at a good rate once the diaphragm starts to fail or other circumstances make the oil to start overwhelming the AOS capacity (oil quality, viscosity, humidity, etc).

c) the diaphragm is sideways (vertical) this creates a problem as oil sticks to it and makes it degrade faster

d) the plastic tubes, and I mean all of them including the j-tube to the throttle body, the one from the drivers side block vent to the AOS are brittle and crap, as they crack just by looking at them. (specially in an old 986 like mine), not to mention the plastic tubes for the dipstick and remote oil fill. (I got rid of those too but that is another story)

e) there is a little check valve in the tip of the driver's side block vent that also starts blowing oil when the system fails and it gets oil all over your drivers side part of the engine.


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.

So that's it
Steve

Last edited by stelan; 01-21-2016 at 05:05 PM. Reason: Forgot
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Old 01-21-2016, 07:37 PM   #13
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Steve ,
That is impressive because you have tested your mod and it works !
Someone else has described using a catch can as a primary 'trap', ahead of the AOS but your creation goes mush further by eliminating other weaknesses.
I hope sometime you'll find the time to write up a DIY guide for this with photos ? Perhaps when you are traveling you will have time?
The pcv you mentioned - is it part # 06A 129 101 A
like this?
New Crankcase Breather Vent Purge Valve PCV Fits VW Golf Passat Audi A4 A6 1 8T | eBay
For the Catch can, the nearest to your description I could find is this:
Universal Car Engine Coolant Cooler Radiator Overflow Breather Tank Can Cap Kit | eBay
or this:
Chrome 800ml Universal Radiator Coolant Aluminum Catch Tank Overflow Reservoir | eBay
or this:
3" x 9" Polished Stainless Steel 32 oz Radiator Catch Can Overflow Tank Bottle | eBay
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Old 01-21-2016, 07:54 PM   #14
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Yes I will make a DIY. That is the pcv valve and the tanks should work either one as long as the fir in the space, In my case I had plenty of room because I do not have the plastic oil fill tube in the way
Thanks
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Old 01-22-2016, 05:27 AM   #15
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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.
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Old 01-22-2016, 05:37 AM   #16
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Quote:
Originally Posted by Jake Raby View Post
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?
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Old 01-22-2016, 05:41 AM   #17
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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.
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Old 01-22-2016, 07:52 AM   #18
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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.

Last edited by Gelbster; 01-22-2016 at 09:05 AM.
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Old 01-22-2016, 08:45 AM   #19
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Originally Posted by paulofto View Post
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.
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Old 02-14-2016, 03:14 PM   #20
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AOS disection photos

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."



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