I've got 98k on my '03 GLS. The upper radiator hose gets hot, and the lower hose stays cold. The upper hose appears to be experiencing high pressure as even with screw hose clamps tightened down well and a new UPR radiator hose, coolant still leaks minutely as evidenced by the white reside. Not enough to drip, but just enough to get a whiff if I get my nose down to it. So I immediately think TStat. Pop a new one in with a drain and fill of new coolant and a few weeks later the same issue persists. The temp gauge moves normally, but never climbs above the midpoint of the gauge. No water in the oil or white smoke, and no loss of coolant or leaks (other than at the upper hose at the radiator junction as mentioned above). I've come up with a couple possibilities but would love to hear other suggestions.
1. Plug or reduction of coolant flow in radiator and/or coolant lines/passages
2. 2nd TStat was bad outta the box