An internal combustion engine having a retarder and a heat exchanger which re-cools the retarder oil, with cooling air being supplied to the heat exchanger during the braking operation. The internal combustion engine is provided with an exhaust conduit in which is arranged a blocking device for closing off the exhaust conduit during the braking operation, with the thus retained gas flow being utilized for conveying the cooling-air flow to the retarder oil heat exchanger.
