ASR...ASR...ASR! Did I mention ASR? My only experience is with a '92, but if you do a search here on W140 ASR problems, plan on an entire weekend to read them all. The problem lies in the fact that the ASR light comes on and the car goes into limp-home mode for any number of reasons, and tracking down the correct trouble can cause you to go half-insane and half-broke. Throttle Valve Actuators seem to be the biggest culprit and buddy they aren't cheap! Then to top it off you can pour hours and dollars into fixing it and think you have it beat, then out of nowhere it can happen again after 2, 3, 4 months. The other problem I had was with the vacuum pumps, particularly the multi-function one under the rear seat. If you have a problem with it and you hear it running...fix it quick or you'll be replacing it, and buddy it ain't cheap (a phrase to get used to when dealing with a W140!). Assuming you get all of the bugaboos taken care of you will own one of the most spectacular automobiles ever built.

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1996 SL320 97K miles
1996 C220 130k miles
1992 500SEL 170k miles <---sold
1986 300E 216k miles <---sold