2 PD tdi questions

Hey,

Recently picked up a 2005 jetta tdi, had a coolant leak from the head to the EGR cooler. I just rerouted the line from the head back to the expansion tank and deleted the smaller lines to the cooler. So my first question is, why is there two sets of lines to the EGR cooler in the TDI. The large lines are like 5/8 and the small lines are like 5/16. Obviously the larger lines are to cool exhaust gases but what are the smaller ones for? Also how common is the manifold being plugged up with carbon on the PD tdi? It was an issue with the ALH motor is my understanding. Thanks!

Clogging is much less of an issue with the PD.

After 250,000km I finally removed my intake and cleaned it only because I was putting on a bigger turbo. It wasn't that bad and probably didn't affect performance.

As for the small coolant lines going to the EGR cooler, they seem to route coolant to the valve housing at one end of the cooler. That valve can be open, to allow exhaust to flow right past the heat-exchanger or closed to force exhaust through the heat-exchanger (the part that actually does the cooling). It looks to me as if the valve assembly is cooled by engine coolant. If it wasn't cooled, it would probably get ridiculously hot and perhaps damage the moving parts of the valve (seals, etc)...

My experience is similar to Mike's. Changed out the intake when doing a turbo. It had some build up, but nothing like the pics you see of the ALH's.