Modern emissions control systems use engine vacuum to suck oil vapor out of the crank-case and into the intake path of your engine.  If you have a turbo or super-charged car, this may be gumming up your intercooler, reducing its efficiency.  Luckily for you an oil catch can may help and it is a fairly easy DIY project. Hopefully this post will guide you, but you’re on your own figuring this one out.  Use at your own risk: no wagering.

Since space under the hood is at a premium on the first generation Cooper S, you have to get creative.  The Mishimoto Oil Catch Can Kit used here is a universal part.  [We now carry an even more compact design can in the store.] The upside is it is much less expensive than others on the market; the downside is you will have to figure out how to fit it to your car.  Besides the Oil Catch Can kit, you’ll need the following from your local hardware and auto parts stores: Bracket, bolts, and nuts; 1/2 inch to 3/8 inch coupling reducer (two of them); zip-ties (you always need zip-ties); and if you don’t like the hose that comes with the kit, you’ll need about 4 feet of 5/8 inch hose. You will also need a hole-saw bit to drill two 3/4 inch holes if you choose to mount the can next in this location. Also get two grommets that fit the holes you drilled and have an inner diameter of the hose you choose.  Expect to pay $10-$12 for all that (more if you have to buy the hole-saw bit.) I found grommets at NAPA auto-parts.  Look for PCV Grommets and then choose the right size.

We chose to mount the can in the passenger side cowl area between the ABS control unit and the firewall.  There is a threaded nub there that can be used for mounting.  Test fit the can and then decide the additional hardware needed to make the connection.  We ended up using two nylon spacers and a two and a half inch piece of metal with two holes 1 3/4 inch apart, but you’ll have to check what works for your application.  We also stuck sticky piece of sound insulation foam on the bottom of the can to ensure it didn’t rattle. Check that your hood insulation doesn’t interfere with your hose placement by putting some chalk on the upper edge of the hose and closing the hood.  Check for chalk transfer to the hood liner.  If you get a little, don’t sweat it.  If you get a lot, try to place the can lower in the cavity or tip it so the hose sits lower in the cavity.

Next you need to be able to route the hoses to the engine.  We drilled two holes through the plastic cowl compartment with a hole saw.  Put a piece of wood behind it so you do not saw into your brake lines.  Space the holes far enough apart that you can fit grommets into each without overlapping. On the left side of the valve cover is the PCV valve. There is a short hose that runs from the valve to a gray vacuum hose that sits under the intercooler. Pull the hose off of the PCV Valve and then cut it as shown by the yellow lines in the picture.  You want about an inch to leave on the gray vacuum line. Insert your reducing couplers and put the hose stub back on the PCV valve, only point the “L” to the left instead of the right. Size your hoses going to the can so they do not kink. Secure with hose clamps as needed and zip-tie so they do not move excessively.  Start your car and listen for vacuum leaks.  If you have a rough idle or you throw a code, you need to check your connections.  Remember to check the can in a few weeks for oil and other fluids.

If you have an ’02-’04 model car and have not installed the cabrio strut braces like we did, you might be able to fit the can next to the motor mount by relocating the grounding wire.  Just check that you can still close the hood without binding.  Some people choose to install next to the radiator reservoir so they don’t have to drill the cowl.  There’s room to fit it, but you have to remove the can when you want to change the oil filter.

There is a second PCV vent in the crankcase that runs directly to the intake tube before the throttle-body.  Some people choose to connect both of the vent valves to the can and draw the vacuum from the intake tube instead of the gray tube (which they cap off.) Some people have no problems with it; while others constantly throw codes.

If you want to try this second method, you’ll need a few extra parts including an additional 2 feet of hose, a T-adapter, and a 3/8 cap. The cap is probably the hardest part to find, but if you contact us, we’ll ship you one for 50 cents plus postage.  The routing in this model looks like the image below:

Removal of the intercooler makes this much easier, but it is possible to install without removing it if you are patient. Start on the left PCV valve and remove the hose that connects to the gray hard hose coming from the supercharger. Cap the gray hose and cut off 3-4 inches of the hose to fit between the vent fitting and and the T. Move to on the right side PCV valve. Use one coupling reducer to connect to the hose coming off of the vent and connect a piece of hose to run the length of the valve cover and connect to the T you fitted in the first step. Position the OCC approximately where you want to fit it and cut the hose from the T to the OCC a few inches longer than needed. Move to the air intake tube and locate where the PCV hose joins it. Disconnect the existing coupling. Fit another reducing coupler and attach new hose to it.  Run the new hose back to the OCC and cut the hose, again leaving a few extra inches. Fit the OCC so it is securely mounted and cut the hoses to length. If you are happy with everything, disconnect the hoses one-by-one and tighten with hose clamps.  Check for leaks.  Also double-check that you have the hoses routed correctly. Many of the newer catch cans are uni-directional so be sure to check the markings on the outside of the can.