TOPIC: Results of using homemade catch can and Air oil separator

Here's 3 pics of the nasty water/oil junk I just emptied from the homemade catch can and the little pvc white drain bottle under my BMW cyclone air oil separator. These two installed in series in the hose coming from one valve cover to the PCV valve/man. vac source. (On this '85 Subaru 1.8L OHC engine the PCV valve is direct to the intake manifold, it IS the vac. source). It was almost a cup in total, spilled some trying to collect it.










This the result of collecting this beautiful stuff w/o being emptied since last Nov. I think the catch can and AOS work!

Tracy G

BTW- I just noticed in my ebay list of watched items, the BMW cyclone black plastic AOS is cheaper now, just $12.50 w/ free shipping, that's cheap! I will try to post the link here.

Well of course the link didn't show!



Well at least this link is a picture of it!

Go to ebay look for prime_auto an ebay store seller, look in category 'other" it's in the second page listed there, $12.50 free shipping. This makes this trick part cheaper than the parts needed to make the homemade catch can separator I use.

One could simply splice it into the PCV hose and fashion a collection container connected to the bottom drain port. Inlet is the lower side nipple, outlet is the top one. Important to use some kind of sealed collection container, especially if the PCV is still connected to man. vac, else you will have a giant vac. leak! IF used in a re-routed PCV system, leaving the bottom fitting open, can lead to dirt/whatever finding it's way into crankcase vent. system. This BMW cyclone separator is designed to have bottom drain fitting connected to an outside closed container, don't just leave it open. This little cyclone AOS is trick, and will work as good/better than fancy expensive ones sold online.

Tracy G

Tracy G

Tracy G

Just a reminder to all, it's fall again. Winter approaches with it's cold, wet and snowy weather. All who have done a PCV re-route, check for signs of oil aspiration in the crankcase ventilation system. As the temps drop, and wet weather returns, remember the possibility of water vapor presence in the system. Look for oil, oil vapor residues, and the tan/brown milkshake goo anyplace in the system, or under the oil fill cap. IT's already a known phenomena to us. An Air Oil Separator setup, catch can, etc. can help to catch and shortstop oil/water in the crankcase system. Those who've been here ahwhile know of my other posts in the Index of how to make your own AOS and or Catch Can setup superior to many of the expensive ones sold online, the ones I've made and installed work great!

Tracy G

Here's pics of what I just emptied from my home made air oil catch can/bottle thing on the Subie. I also got a bit of oil from the homemade drain bottle off the bottom of my BMW air oil separator. Just getting ready for Winter, interestingly I got over half as much as I got last June, when I drained a full Winter's accumulations. I say that cause it's been a dry summer in Reno. The home made catch can/bottle is first inline between crankcase vent port and the PCV/ vacuum source, so it got 99% of the oil/ water crud. The BMW black plastic cyclone AOS is next inline as a shortstop for any that gets past the bigger catch can. Might be 2 ounces total.







I recommend some type of catch can/air-oil separator, esp. for those running the PCV re-route, it works. I'm kinda proud of my catch can design, I incorporated a few different physical methods of separation together. I sold the white one in the pics, made a duplicate to install on Subie, w/ stainless pot scrubbers added inside to increase surface area. I made these separator/collection bottles for about 30 bucks. The black plastic BMW AOS is still on ebay, cheap. I simply got a white PVC nipple threaded on both ends, added PVC caps,(PVC, the white plastic pipe/tubing stuff at the hardware store), then added a 3/8" plastic hose fitting to one cap. A short piece of 3/8" ID fuel hose connects the drain port at bottom of the BMW cyclone to the hose fitting on the white PVC drain bottle. The whole BMW cyclone AOS and white PVC drain bottle could probably be put together for 20-25 bucks, and it's pretty compact too.

For those interested in more info, look in Index in the Service bulletins category, for "home made catch can bottle" and air oil separator, or similar titles, there's pics there too, you'll get the idea if it's new to ya!

Here's a link to an Ebay auction for the BMW cyclone separator, exact same one I use:

OIL SEPARATOR CRANKCASE VENTILATION SYSTEM for BMW E52 E53 X5 4.4i 4.6is Alpina | eBay
Well rats that didn't work, just search Ebay for BMW air oil separator!
Tracy G