I am sure this answer is buried somewhere in these forums , as total non mechanical I have been trying to fix my wifes Mercedes Benz SLK 230K 02/03/1999 registered 2298cc kompressor auto .
Problem : it boils over after being driven only a few miles, the auxiliary fan is not cutting in to cool the radiator then the little radiator indicator comes on the dash . I hard wired the auxiliary fan and it works just fine , I purchased a sensor for bottom of the expansion tank only to discover I purchased a brass screw in type , when I removed the sensor from the tank it is black plastic bayonet fitting type and much longer ( I know I should have checked first ) so should I get one of those ? will that fix it , could it be the management block (the aluminium thingy with fins on it ?) I am trying to start with cheapest option ?