Engine cooling system function diagram for Smart models 451.3/4 with 132.9 engine showing coolant flow paths and major components.

Coolant flow circuit diagram with radiator, thermostat, pump, heater exchanger, and expansion reservoir labeled A through F.

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See all Powertrain figures for the Fortwo (450), or browse the full figure library. Part numbers and callouts are community-sourced and cross-referenced against the manuals — confirm with your VIN before ordering.