Carbonized oil in intake - nearest Number 1 Cylinder - PeachParts Mercedes-Benz Forum

stephenson · #1 09-01-2002, 10:03 PM

Everyone has heard all the horror stories about the 3.5L diesels - can't debate it since mine is OK still, but with that many testimonials there has to be a problem.

I have heard for awhile that one of the potentially replated observations is a tendency to build up carbonized oil in the induction system. So, today, after getting my parts ordered from Phil (usual great job), I removed the crossover to the intake manifold on my 1991 350SDL with 135,000 miles - I don't think this had been done before.

I don't have a baseline, but I was amazed. The round connector just downstream of the EGR valve was about 25% restricted with large chunks of very hard carbonized oil attached ... the round crossover was about 20% restricted and the flattened out portion feeding the intake maniford was about 15% restricted. On removing the intake manifold, there was a noticeable difference in build up at the mouths between 1/ and the remainder - 1 was the worst (even though it is a bit farther from the connection), 2 next and then the others were about the same.

I am assuming this stuff comes from a combination of the oil laden valve cover blow and the EGR's exhaust gas recirc ... is this sort of thing common in diesels? Is my finding consistent or inconsistent with others' experience?

This might explain the 1/2 second loss of power and puff of brown smoke I occassionally get at highway speeds after several hours of driving ... could it be this gunk coming off in large chunks?

I plan on cleaning it all up ... recently, the EGR stopped working

, so that part of the contributing effects has been rendered inop. I am concerned about simply venting the valve cover fumes ... any problem if I run it under the car? Would seem to be a bit on the messy side ... would not mind continuing to rebreath it, but don't want this stuff building up again ... any ideas?

Wasuchi · #2 09-01-2002, 10:22 PM

It will stink unless you vent it to the back or maybe the side of the car. Oil vapors don't smell good.