A Bosch starter solenoid like the ones on 617.xxx engines cannot be taken apart to "polish" the contacts. The solenoid is crimped together and not easily taken apart without ruining it.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked