I purchased my '96 Taco 4x4 with 2.7 4cyl new. It now has 270,000 miles on it. I've never noticed until now, but the lower hose remains much cooler (74? or so surface temp) than the top hose (174? surface temp). I've replaced temp guage sender - it reads normal, as the original did. I've replaced the thermostat - it too opens and closes as the one it replaced. Dealer tells me the cooling system is performing perfectly and there's no need for concern. Can anyone explain why the lower hose (which goes into the thermostat housing) is colder than the top hose by that much difference in temp range? The engine does not overheat, and the heater performs normally.

the coolant goes from the rad. to the block, through the lower hose, then to the heads, then through the upper hose to the rad.

the hot coolant goes from the block/heads the rad. through the upper hose(thats why its hot). then the coolant cools down through rad. then cool coolant goes to the block through the lower hose(thats why its much cooler).

Agreed, sounds normal. Coolant goes in the top of the radiator, is cooled by the radiator, then back to the motor via the bottom hose. If the bottom hose weren't cooler then the radiator wouldn't be working and you would have a problem.