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Oil catch tank


Active member
Some of you may have been reading my threads on on-going maintenance issues relating to oil leaks and/or smells.

On my last visit to the workshop, the Maestro reckoned that with all the wear on the motor after 400k kms, plus the high levels of boost, the crankcase ventilation system wasn’t really up to the job. He suggested some sort of alternative might work better, like an oil catch can or tank.

My research on the forum suggests that the factory system, if properly maintained, is well up to the job for a stock motor, and may also serve well for high-boost motors.

I replaced the pancake valve a little while ago but there’s still a lot of fumes blowing out of the motor and into the cabin.

What does anyone think?
I got sick of the plastic breaking so I ditched the whole system for a dump to atmosphere. Will be going to a catch-can setup shortly.
I think dumping to the atmosphere is the cause of the problem right now, although it's undoubtedly made worse by high boost pressure and worn rings :mrgreen:
Remove pancake from tip, plug the hole going to the block with your finger with engine run at idle. Should suck in your finger and hold down oil cap firmly (vacuum) if it doesnt then one of the following things.
The breather pipe (s bend) - could be cracked- very common, the rubber t piece attached is perished - also very common, the check valve (pcv valve) is fouled and stuck closed, the hose leading from the intake manifold next to the throttle body to the rubber t has perished.
or you have too much venting into the block- like the dipstick tube not sealing well- not as common.

dont be tempted with the 034 motorsport replacement (block breather attachment and billet pcv valve) items as they dont work. stick with changing these parts each 100,000km at a cost of approx $80 in parts, and a few swear words getting to them.

Its a closed system, therefore if you can smell it it ain't closed. (see above)

You never mentioned what kind of filter/airbox setup you run, you need a little bit of restriction in the TIP for the system to work
As for high horsepower motors- the greater the pressure difference the greater the flow, so a factory system works as the boost rises so does the vacuum between air filter and tip, this extra vacuum provides the extra flow required to scavenge the crankcase.
Gee thanks Ed - very comprehensive! I was considering the 034MS kit, but of course they don't make one for the AJL motor and I don't know whether their AEM kit will fit (presumably that's the nearest type). It does at least have the advantage of being made of silicone which means it would last a good deal longer. But you say the kit doesn't work. is that because it operates on a different principle? If so then replacement with OEM parts is obviously the way to go.

I've been very lazy with this sort of maintenance - in fact I don't do a lot of pre-emptive maintenance at all. AFAIK these hoses and most of the valves have never been replaced in 400,000km. Amazing they're holding together at all!

I have a stock airbox and filter, with a VR6 MAF housing. The seal around the top of the 3" TIP as it exits the airbox is not good - in fact there may well be a certain amount of air leaking past the inlet pipe back into the airbox. Seems to work alright - the oil fumes have only started to become evident in the past few months, coinciding usually with an oil leak somewhere. Once it was a hose at the back of the block, last time it was the valve cover gasket. I wasn't driving it for long enough (before the last Refusal To Start) to work out whether this had had any effect on oil fumes.
the 034 motorsport replacement block breather attachment and billet pcv valve items dont work..
The silicone hose part are fine.

If you are using the stock airbox then you should be making enough vacuum for it to work, however a leak that bypasses the filter wont help-
Not sure if this is any inspiration for you, i've started to place a catch can inline with the PCV system. Actually mounted it about a month ago just haven't gotten around to plumbing it in. Only really have to reverse the 3-way block breather adapter and connect one line off to the catch can inlet and one line back out to the pressure control valve (PCV)

This catch can has been sitting in my garage for about 5 years, finally decided to do something with it. The aim is to have it blend in like an OEM part.


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in all my history of modding cars, i have always been a firm believer of catch can setups. But i always prefer to put catch cans in line with the standard vent systems and never chose to dump to atmosphere.
But it is important that you use a proper baffle designed catch can to catch and condense ALL blowby so no chance of any getting back in...
I use a Saikoui Michi one as i think it is by far the best design i have ever seen.

Coincidently just last night i decided to empty my catch can in the S2 for the first time since installing it (probably only done say 2,000km) and to my delightful (albeit shocked) surprise i drained out a crap load of gunk and watery E85 blowby that didnt get to go back into my intake....

Probably a good 200-300mls (thats a 1 Litre milk bottle!!)
So i guess i should probably start emptying it alot more often... :mrgreen:

That's pretty impressive! I'm thinking an inline system has to be more effective than a venting system - if your problem is oil smoke/smell inside the car. Presumably all the gunk in your milk bottle would have leaked out into the engine bay with a vented system, and some of the smell would have found its way into the car.

My research up to now suggests a lot of the cheaper systems don't do much - just admit oil fumes, smoke and maybe particulate matter into the can and suck it out immediately. You need some way of allowing the gunk to settle in the bottom of the can, as well as a valve or tap of some sort at the bottom to drain it out from time to time. Baffles are one way, and there are also systems with something like steel wool in the bottom around which the gunk condenses and then falls to the bottom of the tank.

Do Saikoui Michi still make catch cans? I looked and couldn't find them the other day. Could have been fat fingers at work again... The Provent system also looks good.

Chris's approach sounds a bit like mine - buy some you-beaut part, then spend the next five years wondering when you're gonna get around to installing it :big_wink: . Nonetheless, the simplicity of his approach is an inspiration and I hope it's successful Chris.

I think the logical approach for me with my ancient hoses and valves is to replace the various parts of the crankcase ventilation system first, and maybe go on to a catch tank after that.
Yeah they are still around kermac
here is a link the one im using
S3 Oil Catch Can

They custom make each one (so no off the shelf unfortunately) they let you decide how you are going to mount it and then you can tell the at which position you want the inlet and outlets facing and then what colour and finish also

see below their baffle design


and here is mine mounted.....

So I read up a little, does catch can really reduce carbon deposit build up? I have B8, looking to 034 product.
I don't think a catch can would make a lot of difference on a stock motor with reasonably low mileage. Provided the components are in reasonable shape, the factory crankcase breathing system should cope with oil emissions.

Most of the people who fit catch cans have high-boosting systems (at least twice the factory boost) and often high-mileage motors with worn rings.

Save your money :mrgreen:
kermac i reckon a catch can would still be beneficial on a stock engine because no matter what there would still be blow by on WOT and i would say half (if not most) of the carbon build up is due to blow by on newer FSI engines....

So to answer your question forp, if it was me i would most likely install a catch can (again a proper baffle designed setup) on a newer FSI engine to avoid any carbon build up, especially since the newer engines are all prone to the gunky carbon build up issues.
Hi guys thanks for the info. Warranty is over :D so you know what's next. When I'm not fiddling around the engine I would be massaging the body work so emptying the catch can frequently isn't a problem.

I only heard of a catch can when I moved to Audi, why is it not as common on Japanese platform? Or I didnt pay attention in class.

My car is burning some oil, let's see how much oil it will be able to capture. I have a rough idea of the amount. Will report back next year :)