You must be choking

You recently stated that "The EGR system recirculates unburned hydrocarbon fumes from the crankcase so they are combusted rather than emitted." Not so. You have described the purpose of a crankcase breather system. An EGR system recirculates exhaust gases, reducing rates of cylinder pressure rise and cylinder pressures at part load thus reducing NOx (the primary purpose for using EGR) and combustion noise.

Asked on 4 July 2009 by

Answered by Honest John

Unfortunately, and this is where the trouble starts, the EGR valve setup on many Euro IV engines also vents the crankcase to the same inlet manifold. The combination of soot from the recycled gases and small amounts of oil from the breather mean that over time the inlet manifold, intercooler and turbo get gummed up, particularly on a turbodiesel engine.

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