Toyota Repair: 1994 toyota pick-up 4x4, coolant leak, internal combustion

Question
truck seems to lose coolant while driving,and start to overheat.

Answer
It needs to be determined whether there is an external or internal coolant leak, the first step is to do a cooling system pressure test to see if there is an external leak, if no external leaks are found it needs to be tested for a possible internal combustion leak which could mean a blown headgasket.