The present invention relates to a method for filling a cooling circuit (2) of a motor vehicle (3) with a coolant (4). A simple filling of the cooling circuit (2) with coolant (4) and an increased operational safety are achieved in that the cooling circuit (2) is initially filled with ion-free water (13) and thereafter with a passivating agent (16), and wherein thereafter the cooling circuit (2) is rinsed with ion-free water (13) and subsequently filled with the coolant (4).
The invention, furthermore, relates to a system (1) for filling a cooling circuit (2) of a motor vehicle (3) with coolant (4).