Aside from the other good replies, it might be noted that the 126 body seat bottom was redesigned with two coil springs (one at each front corner. The original didn't have enough stiffness which allowed too much compression of the steel band springs (and they failed quite often).

Replacement (with new)is definitely the way to go.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician