Honda Civic Service Manual: Engine Cooling

Engine

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Coolant Replacement (R18A9)

1. Radiator Cap 1. Wait until the engine is cool, then carefully remove the radiator cap. ...

See also:

Honda Civic Service Manual. Trunk Lid Opener/Fuel Fill Door Opener Removal and Installation
849110 Removal 1. Front Door Sill Trim - 4-Door 1. Remove the cap (A) from the front door sill trim (B). ...