If you’ve been learning all you can about your diesel engine you may have run across other owners installing crank case vent filters, also referred to as “Catch Cans” or “CCV” filters. You may have also read about problems with intake manifold sludge & clogging. These are connected – a CCV fitler may be able to solve intake sludge and clogging problems!
First Off…
Before we start talking about a CCV filter, let just first go over what the crank case vent (aka CCV) is!
All internal combusions engines experience something called “blow-by” when they are running. Blow by is the term that referres to exhaust gases that squeeze by, or blow by, the pistons. Rather than exiting the engine the normal route – through the exhaust – these exhaust gases enter the crank case. A certain amount of this is totally, absolutely normal.
These blow by gases have two important qualities. The first is that they are full of pollution – both leftovers from the combustion event as well as engine oil vapor that is being kicked up by the quickly spinning engine. These gases haven’t passed any sort of filtration or catalyst so they’re really nasty. Secondly, these gases come out a high pressure. This means that the crank case (the inside of the engine, basically) is filled with pressurized, polluted gases.
These gases have to get out, otherwise the pressure will build up to the point of causing the engine seals to fail. But, you can’t just let them out into the air. So, manufcaturers route these gases back into the intake of the engine where they are mixed with fresh air, sent into the cylidners, burned and then pushed out the exhaust.
What Is a CCV Filter?
A crank case vent filter sits between where the crank case gases exit the engine and before they are put into the intake. The main purpose of the filter is remove the oil vapors from the gases so that the gases that make it back to the engine are free of oil vapors. There are multiple ways to do this, but most filters use a combination of a low-pressure area and some sort of filter media to remove the oil vapor.
Why is it Necessary?
The CCV system seems like a good solution to a messy problem…but things go downhill fast when the exhaust gas recirculation adds particulates to this. The result – a nasty, black sludge that coats intakes, flaps and clogs ports.
Can this be fun to fix…yeah, it can…
But largely its a terrible, terrible, nasty job. Worse, some engines have intake manifolds that are very, very difficult to remote (looking at you OM642 and Powerstroke 6.7L…)
Why don’t they install these at the factory?
They do, sort of. The crank case vent itself typically has some sort of limiting feature. On some models it is simply a pressure limiting valve, while others use a centrifuge style vent which is supposed to take out oil vapors. While these may help limit the damage, over 50k or 100k miles these devices are insufficient to prevent clogging.
Ultimately, adding yet another filter that requires service seems to be a bridge too far.
Chosing the right CCV Filter
There are a LOT of options for CCV filters. The industry leading product is from MANN-FILTER, their Provent line. These can be found installed in engines of all sizes, from small automobile to ship and powerplant level. These use a replacable filter media along with a pressure-drop design to encourage oil and moisture to drop out of suspension.
The popular MANN Provent 200 unit also has a port on the bottom for draining or plumbing back to the oil pan, but should not be left open. Most owners choose to connect a hose to the bottom of the provent and end it with a valve. Oil that is removed from the crakn case vapors will collect at the end of the hose and can be drained at the oil change interval. If plumbed back into the oil pan, the oil vapors will drain right into the oil pan elimating the need for draining.
Other brands exist as well, and most are easier to fit/install than the awkwardly sized Provent. Some use metal-mesh style media rather than cellulose filters which filter out less vapor but don’t require replacement. Some popular options include:
