Came time to change my CCV. Because it was plugged. Because I was careless and forgot to do it sooner. Anyway...... This is the oil catch system that is built into the valve cover of my Cummins 6.7 diesel engine. Why does it have one? Older diesel engines simply have a pipe that blows out crankcase gases into the atmosphere. Once it was required for these gases to be directed into the air intake, they knew they needed a way to keep the turbo from sucking oil out of the engine and blowing it all over the charge air system. Pretty much any decent diesel engine that ingests it's own crankcase gases has some version of this. It works. If I pull the hose that leads to the turbo off, it is dry to the touch. This is a true coalescing filter. Even oil vapor ends up trapped and recombined into fluid form before dropping back into the engine. Sorry about the poor lighting. Tonight was the only time I had to do this, so that's what happened. Above you can see the old filter vs. the new filter, and pretty much how it works. You are looking at the bottom of both filters. The large hole is fed crankcase gases by the area under the valve cover. The smaller hole is fed crankcase gases by a hose that feeds up from the actual crankcase and then into a cavity integrated into the valve cover. Neat how they do that. Above is a good look at the filter element itself. Both the valve cover feed and the lower crankcase feed get their own dedicated element that resembles a long and narrow oval of fleece. The elements are open on all sides so that oil may simply drip down into the cavity built into the valve cover. There is a hole at the back of this cavity that feeds a hose returning oil to the crankcase. That hose has a check valve in it so that it can only allow oil to return to the crankcase and cannot allow anything up. It stays a one way street for oil return at all times. You can see the dirty old filter, and the good new filter media of the new filter. Above is the cavity in the valve cover itself. You can see wires going to one of the injectors through the large hole. Above here, we see the all the way in the back of the cavity, on the right side is the drain hole and hose going back to the crankcase. Now, "so just how bad was the old one", you say? This bad: It didn't break up at all until I started messing with it. I tried blowing air through it before I took it apart and it was like trying to blow through mud. Very restrictive. The solids that make up a tiny portion of crankcase gases eventually take their toll on the filter media. As well as age. There is a sensor for crankcase pressure that goes off if it gets too high. My rings are tight enough that it never got that bad, but I did figure out the issue from elevated potassium and low TBN from my latest UOAs. When these things plug, their effectiveness goes down the toilet. Oil gets into the engine after washing potassium out of the intercooler. TBN goes in the hole as well due to poor crankcase ventilation. Immediately after receiving my UOAs, I went straight for the hose coming off of the filter and yep. Oil wet. Nice. There is an unholy mess waiting for me in my turbocharger that I know looks like the devil took a dump into it. The piping and intercooler will need a good mineral spirits cleaning as well. Going to have to pop the intake horn off of the charge air heater and the plate off of the intake manifold to see what I managed to do there as well. Fun fun fun. Might have just found the sorry excuse I need to order up a turbo with a fatter hot side, Steed Speed exhaust manifold, bigger and more efficient intercooler, fancy charge air pipes and connectors, a Banks intake horn, grid heater relocate kit, and Double Shot water injection. ...Ž...Ž...Ž Service life of one of these is 60-70K miles, so it's an easy thing to forget. I won't again. So there it is. If you ever wanted to know what a "real" "catch can" looks like (and why most of the aftermarket ones being sold are of questionable effectiveness due to lack of this level of engineering), there it is!