Method for detecting a leaking point in a heat recovery system

A method for detecting a leaking point in a heat recovery system (12) of an internal combustion engine (1) of a motor vehicle, wherein the heat recovery system (12) comprises at least one particularly combustible working medium and a working medium circuit (13) with at least one EGR evaporator (14a), a pump (15) and at least one expansion machine (16), wherein the recirculated exhaust gas of the internal combustion engine (1) flows through or around the EGR evaporator (14a) which is arranged in an exhaust-gas return line (4), and wherein at least one oxidation catalytic converter (6) is arranged in an exhaust gas line (3) of the internal combustion engine (1), wherein at least one first temperature sensor (30) is arranged in the exhaust gas line (3) upstream of the oxidation catalytic converter (6) and at least one second exhaust gas temperature sensor (31) downstream of the oxidation catalytic converter (6), and the temperatures (T1, T2) of the exhaust gas are measured with these temperature sensors (30, 31) during operation of the internal combustion engine (1) in the exhaust gas line (3) upstream and downstream of the oxidation catalytic converter (6), and a temperature difference (ΔT) of the exhaust gas upstream and downstream of the oxidation catalyst (6) is determined, wherein upon occurrence of at least an abnormally high temperature difference (ΔT), preferably after carrying out a plausibility check, a conclusion is drawn on a leak in the EGR evaporator (14a).