Abstract: An engine exhaust gas purification system has a secondary air system for supplying secondary air into the engine exhaust system. The secondary air system has an air metering valve and a switching valve. The air metering valve is operative to meter the secondary air supply in accordance with signals emitted by an air-fuel ratio sensor disposed in the exhaust system to detect the oxygen content of engine exhaust gases. The switching valve is disposed in the secondary air supply line downstream of the air metering valve to interrupt the supply of the secondary air into the exhaust system during a high load engine operation for thereby preventing the exhaust system and, particularly, the catalyst device therein from being overheated. The force to close the switching valve is strong enough to keep the valve closed against the counter-flow of engine exhaust gases from engine exhaust system back into the secondary air system.