[glend]

A big problem with CRDs is that the EGR system and the crankcase ventilation system combine to make a particularly nasty black mud that coats the intake body, year after year. The best prevention is to: 1- stop oil mist being injected from the crankcase back into the intake. This is easily stopped with a Provent system, and its a great investment imho. I have run one since the first week after I picked up my new CRD back in 2007. During that time it has collected and drained many litres of oil.
2 - stop EGR soot from being pushed back into the engine intake. This is harder to defeat, but an effective way is to run the GDE tune, which deletes EGR. The tune turns off the valve, and only opens it to blow off over boost that might harm the turbo vanes. Now the GDE tune used to do this, but i suspect they may have had to stop it in the US market, maybe here to. In any event I have it on mine and it works. Another method, or hack, is to block the EGR pipe at the exhaust manifold flange, which is pretty easy to do. Combined these two mods will prevent your intake body, and intercooler, from being coated and clogged.
However, in old CRDS that have never had these measures applied, it is highly likely that they have serious restriction in the intake body, and oil sitting in the intercooler. Has anyone here pulled their intake apart to inspect and clean it?
I would like to see a Dino test to compare a clean engine with a clogged one.