I recently traveled from adelaide to sydney via canberra and back. 3 days after arriving home i noticed coolant dripping from under the transmission. At first I thought rear frost plugs {welsh plugs} On further investigation I found coolant flowing down the back of the engine. To cut a long story short the actual leak was a blown gasket between the water pump and the engine block. To fix it unfortunately everything down to the timing belt has to be removed, as well as plenam chamber and inlet manifold. you may be able to change "O" ring on heater pipe and not have to remove inlet manifold