The Mercedes factory crankcase vent was plumbed into the top of the air cleaner into a built in oil catch can. It worked marginal at best. Mercedes cars are like VW Rabbits, they don't leak oil, they are marking their territory. I am not using the factory air cleaner, I opted to use a K&N type filter ahead of the radiator for cooler air and to give more room under the hood. The Mercedes filter is huge and looked out of place on the truck. I plumbed the crankcase vent into the air intake tube pre turbo, but since a diesel has no vacuum, it would not draw out the crankcase pressure. The Mercedes has a vacuum pump on the timing cover driven by the timing chain. The vacuum pump "exhausts" into the crankcase, pressurizing the crankcase and since the engine is turbocharged there is more blowby than with a naturally aspirated engine, that was also adding to the crankcase pressure. The crankcase pressure was causing the valve cover gasket to leak and run down on the sides of the engine and drip on the ground. It was making a terrible mess. I found a smog air pump for an '82 Ford Escort/EXP at Rock Auto that had intake and exhaust ports on it. I made an adapter to mount it on the engine on the power steering mount. I machined a pulley for the pump also. I plumbed it so it would pull from the valve cover thru the oil catch can to the pump, then exhaust thru a hose under the drivers running board. The valve cover is staying dry now. The engine Revs easier and I gained about 2" of vacuum on the vacuum gauge. I think I have negative crankcase pressure or close to it now. Here are a couple of photos.




This is the oil catch can. I had a steel reservoir on it, but I couldn't see if it was catching any oil. I can see that it is working now. When the engine is not running, a check valve opens in the pan and the oil drains back into the pan thru the hose in the bottom of the clear reservoir. I also bought a check valve to connect the pump to the engine exhaust, I may do that eventually.
Thanks, Mark

 

Great engineering!!

 

Very nice! Why not plumb it into the intake? Is the discharge plume noticeable?

 

Thanks Greg and Ross. I was afraid if I kept driving it the way it was leaking that I would damage the front and rear main seals. The rear main is a rope seal similar to a flathead and the crank has to be removed to change it. Running it back into the intake would be easier. I can wipe my finger inside the 3/4" exhaust hose and not get any color on it, so the catch can is catching all the oil. The Mercedes catch can didn't catch all the oil and the inside of the intake had a thick layer of black gunk coating it. There is a faint grey color to the vent exhaust in the right light.
Thanks again, Mark

 

My 2012 Cummins 6.7 has the vent plumbed into the intake right at the turbo inlet. No catch can. Instead it has an expensive crankcase filter under the rocker cover. It works fine for me but, I see a lot of forum posts about eliminating the expensive filter and adding a catch can. Seems a lot of owners get oil inside the turbo and beyond. I don't have that issue. Your idea is the best I've seen. Pretty slick and effective solution. Nice job!

 

Thanks, Scott. Most of the newer cars use an electric secondary air smog pump in place of the belt driven one I'm using. I thought about an electric pump so I wouldn't have to build a mount for it, but I read on a diesel forum that a fellow said he tried that and the electric pump didn't last very long. He said that he found out that the electric pumps only run intermittently and aren't designed to run continuously. Rock Auto had 1 Ford Motorcraft Escort/EXP pump in stock for $24, so I bought it.
Thanks again, Mark

 

Just a word of warning, if oil does manage to get in the pump they tend to seize up. People used to use the factory pumps with racing but moved onto specialty pumps that can handle oil but they aren't cheap.

 

Thanks for the heads up. I will keep an eye on it. How much oil will the pump tolerate? So far the oil catch can is doing it's job.
Mark