We took delivery on a 2004 Sienna LXE AWD in 11/03. In early 7/04, the fan started working overtime, the temp went up, and when I lifted the hood, the right side of the engine compartment was coated in pink spray. The van had about 15k miles on it.
We filled the radiator with water and drove it to the dealer, who immediately acknowledged that the problem was a defective radiator (one of the parts manufactured in the US..

...sigh). They replaced it right away.
According to the dealer, Toyota has known of this for quite a while but is not going to issue a notice. I asked the dealer if there were any other little surprises that Toyota has failed to mention. He said no.
We're going on vacation up to Vt. and Me., and I tell you what, if this had gone bad while we were on that vacation, I wouldn't be telling this story with such a calm voice.
Once the radiator manufacturer discovered the defect, they fixed it immediately (according to the dealer...didn't want to lose that Toyota contract), so it's probably only an issue with early '04 Siennas.
But how difficult could it have been, with computerized parts tracking, to notify customers who bought Siennas with that bad batch of radiators?