got home today and just before stopping steam came up though the back of the bonnet, i stopped and opened up bonnet a steam was coming from back of the engine and the radiator was empty. the temp gauge was on normal and the heater was on at the time. i waited for it to cool down a bit and re filed the radiator and found the source of the leak its on the back of the engine under what i think is the feul filter(glass thingey) it was coming out of what i think was a pin prick hole in a threaded hole about the size of a 2p.its a 1977 s3 2.25 petrol.