The thermostat housing on my friend's Explorer is cracked so it will not hold coolant. On this particular vehicle, the housing is integrated in the upper intake manifold, which neither he nor I are confident in our skills to replace. So he will be taking it to a mechanic. The nearest shop I trust is only about two or three miles of stop and go street driving from his house. Is it safe to drive the vehicle that far without coolant? The engine will not heat up much in that time but I am not too knowledgeable about engine cooling systems and do not know if some sort of damage could result from such a short drive without coolant in the system.