I just bought a 93 sc

Its not the First thunderbird i have owned but it is the first Sc. I was driving it the other day and after a few miles of interstate speed (75mph) at a stoplight i noticed steam coming off the engine. when i opened the hood, i heard the radiator hissing, and being as it was 10pm ( what a great time for a test drive) I couldnt see exactly where it was coming from. my question though, is why does it only spill fluid after a few miles on the highway, but on city driving it doesnt? that and i noticed there was a bit of a miss under hard acceleration around 70. it has 115,000 so i am expecting head gaskets taking a pooh on me soon.

-v-

I'm theorizing here so I don't know if this makes sense in practice:-
Is coolant dripping from the weephole on the underside of the water pump? It could be flowing straight down in city driving, while on the highway the airflow could be blowing it onto the engine, causing steam.

well what can i say i expected a few problems, since i bought the car for $500 and the body is in great shape.