So I noticed the coolant level slowly but consistently dropping on the expansion tank, so I had to take a closer look to see if/where I might have a leak. The typical place where it cracks next to the label on the top looked perfectly fine. What I found was the radiator leaking coolant, apparently out of the lower seam between the core and the plastic tank. This radiator is only 4 years old, bought from the local Toyota dealer. Toyota only offers a 12-month warrantee on their parts, so I'm off to buy a new radiator (updated part number). Has anyone else encountered this failure mode?