Got a 220d AMG Premium Plus and a few weeks after purchase noticed a strange smell of what I thought was plastic melting. Turns out it was a faulty oil seal on the differential. What also seemed to be happening was the front outer wings (fenders) were getting warm to the touch. All was fixed but yesterday the smell was back so booked it in again to be looked at. Anyone else having this issue?
Had the same issue - burning smell and excessive heat under the bonnet & wings. Called MB and they say this is normal behaviour, the Diesel engine is designed to periodically run a 'high temp burn out cleaning cycle' - there is a technical term for this?
Diesel particulate filter (DPF) regeneration is what I suspect you are experiencing. The filter catches soot and every so often it needs to be cleared. The engine management computer is programmed to do this periodically. It makes timing adjustments to the fuel injection system which forces an increase in exhaust temperature to about 600C. This turns all the accumulated soot particles to ash which is expelled thus unclogging the filter. The regeneration typically takes about 10 minutes to run its cycle and usually occurs every 4-500 miles. It will do it more often if you use the car mainly for short journeys where the engine doesn't get up to full operating temperature for long. It is also possible the regeneration cycle won't complete. Sometimes the filter won't unclog and a warning light will appear. If its bad, the engine will go into limp mode to protect itself in which case your mechanic will connect the car to a diagnostics computer and induce a forced regeneration cycle.
The occasional sustained hard thrash along a fast road is always a good idea (my car made me do it, Officer). The 43 guys already know this and they don't even have a DPF >