Pelican Parts Forums

Pelican Parts Forums (
-   Porsche 924/944/968 Technical Forum (
-   -   Info: How to Clean AOS (

Trevorlw 03-21-2013 12:55 AM

Info: How to Clean AOS
A suggested procedure for cleaning the air/oil separator is outlines below:

Remove air/oil separator in accordance with the Service Manual.

Flush the air/oil separator with mineral spirits to remove oil.

Utilizing compressed air, remove mineral spirits from air/oil separator.

Place entire air/oil separator in container of Berryman’s Chem-Dip making sure unit is submerged, and all air pockets have been removed from internal surfaces of the air/oil separator.

Soak air/oil separator overnight for best results.

Remove the air/oil separator from the Berryman’s container and rinse with water.
Utilizing compressed air, remove any water from both inside and outside of the
air/oil separator.
Reinstall the air/oil separator
Check for oil leaks and verify proper operation.

Berryman's Container is just the bucket of Chem-Dip "Carb and Parts Cleaner"
The AOS WILL cause buildup on the bottom of it after age. This would help function and proper usage of the AOS.

Just thought I'd share with you guys, since a lot of people say use water....then Seafoam. This is much more effective. Buy some ChemDip and stick it in over night. Flush and it makes the oil easier to get out.

John_AZ 03-21-2013 03:43 AM

Nice. Thanks for the information on cleaning.

Here is a link that may help new owners understand why the AOS may need to be cleaned:

Oil filler/separator is on a 944 - Rennlist Discussion Forums


Volhv 03-21-2013 06:41 AM

The top "cap" can also be removed, revealing a now brittle o-ring.
It would also be easier to clean it this way.

OzGreg 03-21-2013 09:39 PM

Very timely.

Many thanks


POPS 83 944 03-21-2013 09:53 PM

What size is the o-ring or is it available from the part side???

Volhv 03-23-2013 02:44 AM

The o-ring is not available for purchase. Size is about 80mm OD, and 2.5 mm thickness. The old one can be used to find something that will work.

NAYNOR65 07-25-2013 07:29 PM

968 oil separator cap
Does anyone know how to remove the cap to the AOS on a 968?

gizmoe107 06-03-2014 06:58 PM

For anyone that is interested - the o-ring for the cover is an AS568A-151 size. It is available in hi-temp silicone from McMaster-Carr, p/n 9396K172. A pack of 10 costs $8.09.

I bought a pack and have 9 more left. Rather than trying to sell them, I would like to pay them forward to other 944 owners. If you would like one, send me a pm, I'll give you my address, then just send me a SSAE and I'll send you one until I run out.

Jrboulder 06-03-2014 07:02 PM

The question I have is why bother cleaning the AOS?

v2rocket_aka944 06-03-2014 07:26 PM

perhaps to help oil drain better at the bottom?

but there's really nothing at all inside of it. it is just a can with a few holes in it..

88Silver924S 06-03-2014 10:02 PM

Silicone Viton or Nitrile for o-rings
I was curious about the different o-ring materials since there are so many & found Chemical Compatibility Guide. Comparing Silicone and "Motor oils" returns "Good" but common Nitrile (NBR) or Viton (FKM) both come back as excellent. I'm no chemist, just passing along what I find. I thought silicone would be better, maybe not? Am I missing something? Just trying to learn something new.

wayne986 06-04-2014 03:43 AM

Smoke at Start up
Can this cleaning procedure be used on 2001 986 boxster as well?

v2rocket_aka944 04-11-2015 06:59 AM

BUmping this up for the records and future searches...

McMaster-Carr pn# 9396K172 (as mentioned above) is a perfect fit for the 944 AOS. (Unit shown is an S2 AOS)
See attached photo! (You only need one but I wanted to show fitment on both sides)

Annie Datkinson 09-25-2018 12:50 AM

I've found this website to be really useful.

Plenty of information about O-rings and you can receive a quote off them by calling them up.

Swennydawg 10-03-2018 11:12 AM


Originally Posted by Jrboulder (Post 8098053)
The question I have is why bother cleaning the AOS?

The idea of an oil and air separator is to extract the oil from the air before it's sent back to the intake manifold and put it someplace where it won't cause a problem,like the crankcase. If it's goobered up or if the seals fail it'll most likely end up in the intake system. Just a small amount in there will put a frown on your face.It's a mess to clean and needs to be on the same service cycle as the timing/balance shaft belts. Cleaning and changing two seals at a nominal cost and while you're there the dipstick seal. When you start sucking oil,you'll know it!

v2rocket_aka944 10-03-2018 11:49 AM

^^ a little smoky, but your valves have never run quieter/smoother 8-)

RubberDude 01-30-2019 06:54 AM

I use this website whenever I need to replace any of my existing O-rings:

This Chemical Compatibility Guide is also a good tool for breaking down the qualities of each type of sealing material for o-rings so you know exactly what you're getting. Hope this helps!

kolll 06-12-2019 05:24 PM

that is what I find in the bottom hole of AOS on my 944
what the heck is that:confused:
is there any membrane has to be inside?

theer 06-13-2019 07:22 AM

Tirez is French for "pull", so that's definitely not OEM!

The hole in the middle looks like it was made with a Phillips screwdriver. Could be a top from an oil additive someone was squirting in there and the lid popped off...?

All times are GMT -8. The time now is 08:52 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.