as some of you may remember, i had a failed motor mount problem on my 550 last summer. others here have had this problem as well. i was cleaning up the garage this morning and wanted to post some pics so folks knew what to look for if they want to inspect their mounts. this was easily the most annoying, painful, and frustrating automotive mechanical problem i've ever encountered. so i saved the damn things as a "souvenir of my pain" . yes, i'm less than normal - but you already knew that . grossly simplified, basically, the part is metal conical structure surrounded by another larger metal conical structure, with rubber in between. what happens is (at least in my case - i assume this is the standard fail pattern but i could be wrong!) that the interior metal cone separates from the rubber between the two metal structures, and eventually this lack of "support" for the engine can result in the engine, in various circumstances, touching or resting on the frame the rubber is intended to keep it off of. so you get all sorts of weird vibration transmisisons. the first picture is just a snap of the two mounts that were replaced in my car. they are about 11cm by 9cm by 5cm high. in the second picture you can see, around the interior metal circle, along roughly top and bottom ~120 degrees of arc how the rubber has split. these motor mounts are the topic of FNA TSB # 1041 "Engine Support Rubber Bushing" dated February 2003 (PDF attached). at that point they redesigned the part so it wasn't, well, ****ing stupid . you can see that the new part makes more engineering sense (at least to a non-MechE like me). fwiw, the anecdotal data on this board seems to suggest that cars driven very frequently develop the problem less often. in addition, the anecdotal data suggests that your authorized FNA dealer will replace them gratis if they fail. no guarantees on this! it's NOT the subject of a recall - but most folks here who have had problems have had them replaced gratis - whether it was automatic or it required some *****ing at FNA in NJ. hope this is helpful to someone someday! doody.