Oil Catch Can: Updated!




Always a tinkerer, never an inventor... I like to spend my time coming up with better, more effic...

So, my blue headache (bmw 318ti) started having some idle issues.  Being excessively cheap, I decided to attempt a DIY fix for my problem.  After reading numerous forums, I've found the culprit to be the PCV/ECV valve.  This particular part is used to recycle some of the valve cover gasses to maintain some semblance of "emissions standards."  However, when excessively worn, the valve allows extra air into the intake causing idle and fuel/air mixture issues.

Well, I don't live in a state that has emissions tests any more, so let's bypass that sucker!

DISCLAIMER:  modifying engine components can and will void any sort of warranty (not that anyone on this site is worried about that).  Working on cars is dangerous, accept that you will get burnt, crushed, sliced, diced, and killed.  With that in mind, watch your digits and be careful.  I accept no liability for any modifications that cause engine failure, engine explosion, or cause the engine to disappear into another dimension.  Nor do i accept any liability for personal injury, unless there is a wormhole involved, then it's totally my fault.

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Step 1: Get the Parts Together

There is a lot of leeway with the actual materials list on this one. 

I used:
1x small paint can and lid     (this can be substituted for any container, though i'd recommend metal)

1x coupler to fit hose

1x nut to tighten coupler

Length of hose (determined by the size of your engine bay)

Tie Wraps to mount can in engine bay

Drill with bits appropriately sized for coupler and vent holes

Step 2: Drill the Lid

It's a pretty self explanatory step, so let me use this time to give you the 'why' of this project. 

The point of a catch can is to allow the valve cover to vent any excess gasses and oil particles without dumping them directly into the environment.  The can gives the gasses an opportunity to slow down and let the oil/carbon particulates fall out of the stream and stay in the can.

The PCV would normally route these to the intake manifold, however mine is constantly stuck in the open position causing idle issues.  I don't feel like spending 50 bucks on yet another piece of plastic, so we'll plug the intake hole on the PCV and call it good.

Step 3: Attach Coupler and Hose

This step is 'overkill' in my book, but it makes it look better and feels a little more permanant. 

Push or screw the coupler through the center hole in the can and attach the nut to the opposite side to hold it in place. Push the hose onto the coupler and (if you're feeling frisky) attach it with a hose clamp.

If you don't have a fancy coupler you can just push the hose into the hole in the lid and that should work fine, perfection is not required here!

Step 4: Pop on the Lid!

Press the lid onto the paint can and you are finished (as far as assembly goes)!  Congratulations, you've just created a bypass to the environmentally friendly countermeasures on your car! 

I have not installed this as of yet, but will update with pictures and results when i do.

Please vote for this in the Jury-rig It Contest!  (I was going to put this in the green contest for laughs but decided against it) 

Step 5: Update: Installed

The pictures and tags pretty much show the installation in full.  Except for putting the PCV Hose back on (pop it back on the exhaust on the valve cover) and routing the hose to the can (I used a long hose so i could reach around the engine bay to keep it in the cooler areas).  But those would be different with every engine. 

Anyway, thank you again for reading, and after i give it a run-in I'll post another update!

And a belated apology for the cr*ppy pictures, my camera phone sucks :(

Double Update Action!!!!!!

    the way I had the hose routed to the can as shown in the pictures was the wrong way to do it.  Some of the gasses remain in the hose, cool down, and create a liquid plug if there are 'ups and downs' in your line.  Now i have it draining straight down.  We'll see how it goes!

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    8 Discussions


    6 years ago

    Deleting of the PVC system is going to make your engine were out quicker. The intruded purpose of the PVC system is to combust the crankcase gasses that accumulate, if they are not able to be sucked out and combusted it can start to corrode the rings in your motor. Then your headache turns into an even bigger headache. Not to mention the fumes you will have in your cab, that's a literal headache.

    5 replies

    Reply 6 years ago on Introduction

    Plugging the PCV system would damage the engine, but he's not plugging it. He's only plugging the intake end, and allowing the blowby gasses to escape into the can and the atmosphere. The damage (I think) would happen if he plugged the exhaust end of the PCV system, which would allow pressure to build inside the engine cases and cause damage.


    Reply 6 years ago on Introduction

    correct, plugging the exhaust (coming from the valve cover) would cause an increase in crankcase pressure which is bad. Plugging the PCV intake just gets rid of some (hopefully all) instability in the idle


    Reply 6 years ago on Introduction

    The vent holes in the top of the can are intended to allow the gasses to escape while trapping the oil. And as far as the fumes go, my leaky exhaust puts the valve cover to shame lol. I do appreciate the feedback though and will add a disclaimer that i meant to put in there. Thank you for reading!


    Reply 6 years ago on Introduction

    Well that's definatly better then just plugging it off, I do believe I have seen another design on oil catch cans that connect through the original PVC system too catch the excess oil and yet still suck the fumes into the intake. From what it sounds like longevity probably isn't in this cars future anyway :lol:
    Good idea on the disclaimer, definatly better safe than sorry.

    Thanks for the nice reply.


    6 years ago on Introduction

    depending on how bad your headache is, make SURE to check that can often.

    I have seen catchcans for 1.3L engines from the 90's that the owners were emptying every few thousand miles! Even know of one fella that used his catchcan to tell when he needed more oil, instead of his dip stick!

    If you install a drainback system to get your oil back into the engine, stick a harddrive magnet on that can. Makes for a great place to remove iron particles from your oil to keep your filter working better, longer.

    1 reply

    Reply 6 years ago on Introduction

    I will be checking it frequently, and included a wrapped up absorbent pad to prevent sloshing. I probably won't do the drainback system unless a very large amount of oil is collected. And good call on the magnet, I put one in the oil pan for just that reason. Thank you for reading! be sure to vote ;-)