papaindigo wrote:
Folks before we get too far into the conspiracy theorist weeds I'll try a bit of history. All internal combustion engines since they were first invented produce a certain amount of blow by, past the piston rings, which results in pressurizing the crankcase and that excess pressure has to go somewhere. From the invention of internal combustion engines up to just past the middle of the 1900s that pressure was simply vented to atmosphere (EHM does this which is why it smells bad and smokes) which studies indicated produced about 50% of the atmospheric (a.k.a. smog) hydrocarbons produced from internal combustion engines. Beginning in the 1960s positive crankcase ventilation valves (PCVs now called CCVs) began to be fitted to all internal combustion engines as far as I know pretty much world wide. Back then at least on gas engines the PCV system was a simple crankcase hose fitted to a one way valve in the inside of the air filter such that crankcase gas was simply vented back into the air intake stream to be burned. Other than occasional air filter contamination this causes no engine problems. IMHO the CCV on the CRD engine is BY ITSELF harmless but for the bad impact on the air box to turbo and CAC hoses which DCJ engineers in their wisdom did not make oil resistant/proof.
Soot while a related animal is a different problem and as far as I know is related almost entirely to adding exhaust gas recirculation in one form or another. Exhaust gas recirculation is "supposed" to further reduce smog by recycling exhaust gas into the intake to capture and burn any hydrocarbons that exit the combustion chamber, unburned, into the exhaust system. As we all know soot is a bad thing for a variety of reasons. While I cannot speak for other engines I do think the CRD soot problem is largely caused by plumbing the CCV vent just in front of the turbo which sends some amount of oil mist thru the turbo and intercooler (bad for hoses) thru the FCJ and past where the EGR injects hot exhaust gas into the intake. I suspect the soot is created by the exhaust gas at that location vaporizing the oil mist leaving behind some unburned mist and the soot that was suspended in the mist.
Bottom line - don't blame the CCV rather blame the EGR and the direction of flow from the CCV. I suspect that if the CCV was plumbed directly into the intake somewhat past where the EGR connects that the soot problem would largely go away. Absent fixing that, which I'd call a plumbing design flaw, the only solutions are a) get rid of the mist which cannot be done by plugging the CCV (we know this because a frozen EHM tube will and has blown the rear main seal) but can be done by venting to atmosphere (not good for the environment) or venting to a filtered catch can (much less bad for the environment but still lets some hydrocarbon vent to atmosphere) or b) reducing or eliminating EGR flow.
No dealer, at least in the US, that wants to stay in business will install a CCV catch can that vents to atmosphere as that violates one or more Federal anti-pollution laws. That said it might be possible, I'm inclined to doubt it absent some evidence of EPA approval, for a dealer to legally install an inline catch can that maintained the connection between the CCV and the CRD's air box to turbo. Doing the latter, seems to me, is no more than adding a filter into to CCV line to catch some of the oil mist and would be harmless from a pollution control perspective.
There are plenty of catch cans that don't defeat the purpose of the CCV. One of the common mods over on the GM forums is a catch can inline with the stock CCV routing. They condense the oil vapor out before it enters the intake and still maintain a legal emissions system. They do it to keep the intakes clean as well as prevent the oil vapor from lowering the combustion threshold so they can advance the timing. I am not sure i buy the second point, but thats what they say.
This problem is not exclusive to our engine though. I have done quite a bit of research on the BMW 335D(3L inline 6 diesel) and they suffer from worse EGR/CCV issues than we do. I hear the same thing with VW TDI's too. Maybe they don't do it because there are other things in the blow by(combustion gases) that they dont want getting back into the engine oil and know that the average schmuck won't empty it every month.