hi there, i recently purchase a 1998 VW Passat at car quick in San Diego for my little brother for college, the Passat look nice and drive nice and it has 140k miles on it but the only problem the engine overheat so quick in less then 5miles it start smoking and you have to stop the car. the engine is 4cylinder Turbo Engine and I check it but I'm not an experience mechanic and i can only fix and know a little about Japanese Car like Honda and Toyota since i own them but i do not know so much with German car. this is the first German auto brand we own in our family so this is like a new experience for me and i know the best way to finding out the problem is by taking it to a experience mechanic shop and i ask my brother to take it to my friend auto body shop for an oil change and they told my brother the car needs a transmission services, front driver axle, tune up and front break need to be replace, now i did and replace the front breaks and now I'm working on the tune up but can't do the driver axle and Transmission. so the question is what makes my brother VW Passat engine overheat. I was thinking maybe head gasket, water pump, radiator maybe need services, or maybe the fan but the fan is working properly and also thinking maybe cooling cause when i add an anti freeze coolant to the top and now it have way down and its only three days now. so please help me, any suggestion will help so that i know what's going on so the mechanic doesn't charge me much. thank you for all your help.