Gas Recirculation Valve (egr Valve) problems of the 2007 Mercedes Benz ML320

I purchased a used 2007 mercedes Ml320 cdi on March 12. After a week of driving - I inspected the engine compartment (I usually do). I noticed engine oil dripping (small but noticable amount) on the serpentine belt. I did not think it was urgent - so I took pictures so I can send it to my seller to claim warranty. On March 23, I was driving with my family on I-65. Suddenly, steering became very hard. It was a curving highway so I was forced to go into other lanes. Lucky, traffic was not heavy so I did not swerve into any other vehicle. I was able to wrestle with the steering wheel on time to move away safely. Also, at the same time we lost steering, the battery light went on. After stopping, we popped the hood and immediately noticed the same belt mentioned earlier had disintegrated into several pieces. We called for a tow vehicle. Mercedes benz fixed the problem for $300 and assured me that there is no oil leak. 200 miles later, I got home - and saw the same leak, same spot. Oil was dripping from from the turbo to intercooler hose joint (which was just above the serpentine belt). I did some research on the internet and the only similar issue I found led to dtb s-b-09. 20/29. I asked mercedes, but they say its not covered under warranty. So I am currently researching to fix this problem permanently.