This video details the common issues you may run in to with an LB7 Duramax. The LB7 Duramax was the first generation Duramax that spans from 2001 to early 2004. Later in 2004 the moved over to the LLY.
HERE ARE THE TOP 3 ISSUES:
Water Pump Failure
Blown Head Gaskets
Bad Injectors & Injector Location (Under Heads)