Couple months ago I renewed the radiator with new hoses and thermostat. A coolant leak developed and I thought it might have been the hose clamps as there was pink residue at the lip of the hoses (might still be as I have not buttoned up everything yet , will report back). Close investigation revealed that the leak was coming from the hard plastic inlet tube that connects the upper hose to the thermostat. There was seemingly a crack at that point where the hose is attached and when i removed it it broke at that point.. It left a piece of the plastic tube in the radiator hose which I meticulously removed. Once I removed all screws securing the plastic inlet tube to the thermostat housing (3x10mm nuts) it became a challenge to remove it and the trick , in addition to repositioning some wires in the area, was to loosen the starter and pull it out a bit. This provided enough space to remove the inlet tube.
So guys and gals , my sienna is a 2006 le. If you plan on renewing the rad , thermostat, hoses , consider renewing the water inlet plastic tube and save yourself a future headache . Part number 16321-0A040 , $42 . Don't forget the pink HOAT longlife coolant as stated in the manual.
FYI , remove air box , air intake assembly , no need to remove battery but disconnect negative terminal. Be safe. Hope this helps someone.