Toyota Repair: 1995 Toyota 4 Runner losing coolant, losing coolant, coolant tank

Question
My son has a 1995 Toyota 4 Runner SR5 V6 with an automatic transmission. It has 143,000 miles on it.  For some reason, it is losing engine coolant, but it is not leaking from the radiator or either of the radiator hoses.  Neither is it blowing out the auxiliary coolant tank up by the firewall.  Could it be getting into the exhaust system or leaking slowly from a cracked water pump and evaporating on a hot engine?  I haven't taken it in to a repair shop yet.  I thought it might have a cracked head gasket, but the engine is running fine and does not appear to be trying to compress and combust water in the cylinder. Any ideas?  Thanks.

Answer
I doen't sound like aheadgasket problem if the engine is not overheating as long as there is coolant in it, unless there is an external headgasket leak, this is usually visible at the rear of the cylinder heads. Another kind of common small leak is the coolant transfer pipe that runs under the intake manifold, a small amount of coolant usually evaporates from the engine heat you would have to remove the manifold to inspect, a water pump leak is also very possible and a removal of the upper timing cover for inspecion of the pump would verify this condition.