Well, I had a jdm front conversion done roughly a month ago where a 2nd hand radiator was also installed, flushed and filled. It was good cond. Done by the boys at Bel Garage.

It has worked perfectly for about a month, no problems at all, highways and city driving.

No idea where all the coolant went when it overheated.., but it was gone. Ive driven the car twice since then and it has over heated like the first scenario and water has had to be put in. Each time I put water in, the Radiator is empty and fluid bottle aswell. Radiator Hoses are very hot aswell.

Possible Crack/leak in Radiator? .. but Im not sure.. came here for advice before I head to the mechanics..