I've noticed a slow leak of coolant from the top of the engine as it cools down. It hardly leaks at all when the ambient temperature is high (like in summer). It seems to come from somewhere between the thermostat and the alternator, but very difficult to access. It starts at the very front of the engine block and then flows down a slight slope (perhaps because of the position of the engine or the car). I've changed the water pump and re-sealed the large pipe from the radiator to the engine. Do you have any idea where this is coming from? Thanks