Anatomy of an OEM Oil Catch Can (CCV Filter)

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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.

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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.

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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.

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Above is the cavity in the valve cover itself. You can see wires going to one of the injectors through the large hole.

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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:

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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!
 
Very good write up. I had no idea diesels had these. How many miles on your Cummins for the filters to get like that?
 
Originally Posted by carviewsonic
Very good write up. I had no idea diesels had these. How many miles on your Cummins for the filters to get like that?


Almost half a million on my engine.

112,000 miles on the filter.

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Not all emissions diesels have them. Powerstroke 6.0 just has a baffle box with a tube coming out of it that goes straight into the intake tube.
 
Nice write-up. I wonder how many people have no clue the filter exists, let alone know it has to be serviced.
 
Yet all the catch can advocates fail to realize or accept that a coalescing type filter is the only real way to separate oil from the air be it from a compressor or vehicle PCV system. A catch can with no coalescing filter is nothing more than a particle/water trap, not very effective.
 
Pretty much. The PSD 6.0's CCV "filter" (baffle box stiffed with steel wool) eventually gave way to a coalescing filter like mine in the later PSD engines.

A lot of companies have a Provent coalescing filter (the only catch can that actually works) retrofit kit for the PSD 6.0 for this very reason.
 
How come the diesel engines have this, and gasoline engines still use a crude system for PCV? I recall seeing a bare vent pipe on trucks and buses that would spew crankcase vapors.

Honda tried to use a gas/liquid separator on the R18 Civic engines, and Subaru did something similar. Both have issues with the oil/air separator plate leaking. Those were a labyrinth design that caused oil to separate via deceleration of the air path.
 
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Originally Posted by nthach
How come the diesel engines have this, and gasoline engines still use a crude system for PCV? I recall seeing a bare vent pipe on trucks and buses that would spew crankcase vapors.

Honda tried to use a gas/liquid separator on the R18 Civic engines, and Subaru did something similar. Both have issues with the oil/air separator plate leaking. Those were a labyrinth design that caused oil to separate via deceleration of the air path.


Gas engines do and some can have a cylonic separator which works well. Fortunately for gas soot less of a problem.
 
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Yet all the catch can advocates fail to realize or accept that a coalescing type filter is the only real way to separate oil from the air be it from a compressor or vehicle PCV system. A catch can with no coalescing filter is nothing more than a particle/water trap, not very effective.
I've used them for years but I consider them oil fume condensing cans and locate them outside the engine compartment in ambient temp air. They are very effective this way.

This is typical after 5k miles in the humid summer. And it's from a turbo engine.

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This thread represents all new stuff to me. Yes, I had heard of "catch cans" between the crankcase and intake system.

My multi-question is: Has the science of these filters / catch cans / oil reclamation systems been accepted by the world yet? Is there a company which offers these systems -or improvements to these systems- to augment badly designed ones?

Is there a list of engines which need these things? Seriously, what does a vehicle owner need to "do next"?
 
The Mann Hummel Pro Vent catch can system is very highly regarded in Australia, and I have one fitted to my Outlander diesel. I drain it every 5,000km and it always has 300-500mL of "stuff" in it - water (condensation) and stinky diesel oil (fumes).
 
Not sure what the older ISB6.7 engines had for mileage intervals but the 2013 to 2018 run about 108,000km and then the service reminder gongs you.

Mine was pitch black and saturated but my turbo inlet was quite clean. In fact it looked the same at 24k as it did at 108.

In Canada those filters, Fleetguard CV52001, vary wildly on price. 200$+ at the dealer to just under 100 when on sale at Cummins.

A local kids never changed his and was at approx 200,000km and blew out his main seals because he never changed it.
 
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