A method for detecting a leaking point in a heat recovery system of an internal combustion engine of a motor vehicle, wherein the heat recovery system includes a combustible working medium and a working medium circuit with an evaporator, a pump and an expansion machine. The recirculated exhaust gas of the engine flows through or around the evaporator which is arranged in an exhaust-gas return line. At least one oxidation catalytic converter is arranged in an exhaust gas line of the engine. A first temperature sensor is arranged in the exhaust gas line upstream and a second exhaust gas temperature sensor is arranged downstream of the oxidation catalytic converter. Temperatures of the exhaust gas are measured with these temperature sensors during operation of the engine in the exhaust gas line upstream and downstream of the oxidation catalytic converter. A temperature difference of the exhaust gas upstream and downstream of the oxidation catalyst is determined, wherein upon occurrence of an abnormally high temperature difference a conclusion is drawn on a leak in the evaporator.