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Fumes in cab could be a split EGR pipe. Have a read of this…
I seem to have what I initially thought was an exhaust leak, but after further investigation sounds more like an air leak round the right rear back side of the engine. I wouldn't ordinarily be concerned and just get it into VW to looked at. (It's actually the first issue I've ever had with my...
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Or could be a DPF regeneration - the fans run while it heats up the Diesel Particulate Filter to several hundred degrees C which usually creates a smell. Usually does this when you stop and switch off. It also does regens while you’re going along but these are not normally noticed.
Ian