The invention relates to a cooling system (10) for fuel cell stacks (22, 26), comprising a first cooling module (14) and a second cooling module (18). The first cooling module (14) comprises a fuel cell stack (22, 26), a supply line connection (30, 34) for connecting a supply line (38, 42) for supplying coolant to the fuel cell stack (22, 26), a discharge line connection (46, 50) for connecting a discharge line (54, 58) for discharging coolant from the fuel cell stack (22, 26), and a venting line connection (94, 98) for connecting a venting line (102, 106).