One problem related to radiator has been reported for the 2007 Toyota Sienna. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2007 Toyota Sienna based on all problems reported for the 2007 Sienna.
After a short trip, 5 miles, I was backing into my driveway when I noticed some fluids on the cement. I checked the liquid and was not sure if it was coolant or transmission fluids so I called my mechanic and he recommended that I should have it towed in . It turns out that the problem was that a connector at the bottom of the radiator cracked and was mixing the coolant with the transmission fluid ,it appears that a defective fitting was the problem. It cost me $977. 3 to replace the radiator and flush the transmission. My mechanic said if I would have continued driving with these 2 fluids mixing I would have damaged the transmission beyond repair for a bill of $3,000. More if this is a common problemon these cars people should at least be notified what to watch for or better yet repaired by the company.