My SDL came to me with a "brand new" Auto-Zone starter in it. It worked fine for roughly a year while I worked on getting the car back on the road, but then it started hanging up and not engaging the switch for the motor.

The internal rebuild of the motor was fine, but they phoned it in on the solenoid. Whoever rebuilt it slathered the plunger with very heavy axle grease and was just seizing the whole mess solid. Cleaned the grease off (the plunger is supposed to be dry!) and it hasn't given me a single issue since.

If you do go the O'reilley's route, it's worth pulling that solenoid and checking it before you install it. The 617 isn't as easy to pop the starter in and out of as the 603.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]