the water temp above ambient shows that your rad is fine. thunderbirds do get really hot, even with decent watercooling products eheim 1250 cyclone 2 and silverstorm 2 radiator
www.silverprop.com, i cant overclock my thunderbird 1.4 much in summer or else stability problems on hot days (ive seen room temp as high as 41C!! on a 44C day so its not much of a problem cause its too hot to use comp much anyway) however that water temp seems too low makes me wonder if your block is mounted properly (my water temps r normally about 3 or 4 degrees C above ambient)