We are having trouble with my daughter's car. It overheats in traffic but does not seem to on highway. We have checked the radiator level and filled it but after a short while it needs refilling but we cannot find a leak anywhere. We thought she might have blown the headgasket when it first overheated but the car does not blow white,smelly cloud nor is the oil milky. It also sort of surges when idling.
Any ideas anyone?