The radiator is built into the leading edge of the wing between engine and and fuselage. The rad consisted of glycol cooler, oil cooler and cabin heater built into one block.
Stuart Howe, De Havilland Mosquito, An illustrated History, Crécy Publishing, 1999
The construction of the first De Havilland Mosquito was done in great secrecy in Bay 3 at Downsview. This was the first actual photograph taken and shown publicly. This was the first of 1133 Mosquito cnstructed in Toronto. Two Avro Ansons (of 375 also built there) are in the background.