Never heard of a broken piston on a 103 motor.

Hardly ever see compression problems, but they are usually valves.

A proper professional solution to a piston problem will be about as much as the car is worth. A proper overhall would easily cost over $4000. Disassembly and reassembly will cost from 30-40 hours depending on whether you do anything once inside. It of course would be silly to buy those hours and do nothing so the upper limit is more logical. I know a gas station that charges $50 an hour. I doubt they would be foolish enough to do a MB, but it happens all the time. After all motor overhaul is about the easiest of mechanical jobs.

The economic solution for your described problem is a used motor. Done under a shade tree, it could be handled for less than a grand, possibly.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician