if your radiator is gone, it can cause all sorts of problems. first you will get either the car loosing water and the car engine will start to overheat. if the engine overheats to much your head gasket can go. ( i hope yours is okay). take of the oil filler cap and see if there are any signs of water mixing with the oil. you will see a white creamy gunge, like mayonnaise in the inside of the filler cap. if i was you i would check that the head gasket has not gone before you start to buying part to fix it. and dont bother flushing a radiator that is half rotten, the radiator needs replacing.