When using radial engines it's engine cooling flaps than can be adjusted by the Flight engineer to control temp that is the equal of as thermostat. In as much as the temp of each individual cylinder can be monitored it's easier to spot overtemp problems. Our most common problem was from Gooney Birds going through the prop and blocking airflow between two or more cylinders. Other than that, the 3350-42 series was fairly cooling problem free.
ALL internal combustion engines are, basically, air-cooled. It's just that our engines use a liquid coolant as an interface between the generated heat of the engine and dissipating that heat into the air with a radiator. Ditto for oil and oil coolers, it's all about air.
We were towing all over the Colorado Plateau this past month, even with outside temps well into the very high 90's, were never for more than 10 degrees over normal temp, but we did see any number of late model vehicles pulled over from overheating, most often, IMHO, from not heeding the need to monitor speed and temps when driving.
On the leg between Prescott and Quartzsite, AZ, with temps over 115 degrees we didn't get more than 15 degrees over normal on the longest grades, but obviously many others did...
BTW: I drive 55...