The turbos on the V6 and V8 diesels do get very hot indeed. There should be an instruction on a plate somewhere warning you to idle the turbos before switching off when they are red hot, which they will be after ascending a long incline or after towing and which they can be after a long run on the motorway. No such warning on a plate on the car or in the handbook, then I think you do have a claim against the supplying and servicing dealer, as long as it is the same dealer.