The first run of BigBoys out of the Alco Locomotive Works were equipped with air cooling piping that ran the length of the pilot deck, supported on the top of the deck. This worked, but was inefficient.
Later on, Wilson After-Cooler radiators were placed behind a grill low on the pilot deck. They were standard equipment on the Union Pacific's Challenger 4-6-6-4 engines, and were adapted for use on the BigBoys. They worked a lot more efficiently, cooling a larger volume of air per given block of time.