Радиатор течёт

The radiator leaking, from a corroded core, a split plastic end tank, or a failed crimp between the two. The tank-to-core crimp is the commonest failure on modern radiators, where a plastic tank is crimped onto an aluminium core over a gasket that hardens.

Stone damage to the core is the other route, since the radiator sits behind the condenser at the front. Look for coloured residue along the crimp line and at the tank seams, which marks a leak that has been evaporating for months. Pressure-test cold — a crimp leak often only opens hot and under pressure. Where the coolant has been repeatedly topped up with water rather than the correct mixture, internal corrosion is likely too, so check for blocked tubes while judging whether to repair or replace.