Method and apparatus to cool the cooling air for turbine engines

A cooling air cooling system (40) is selectively operable to reduce fuel gum deposits within the cooling system when a gas turbine engine (10) operates above a predefined percentage of rated engine power. The cooling system includes a re-circulating loop (46) including a plurality of heat exchangers (50, 52) in fluid communication with the re-circulating loop. A first heat exchanger uses heat transfer fluid to cool cooling air (42) used by the gas turbine engine. A second heat exchanger is a steam-fuel heat exchanger that uses combustor main fuel flow (44) to cool the heat transfer fluid circulating in the re-circulating loop.