All 2.5 GHz dual processor and all 2.7 GHz dual-processor and the 2.5 GHz quad-processor variant had a liquid cooling system that consisted of a radiator, coolant pump, and heat exchangers bolted to the processors. The cooling system was made by Delphi Automotive, a former Harrison Radiator Division of General Motors. This was a bold step for Apple, and should have allowed the use of very fast processors, giving Apple an advantage in both the performance and reliability race, but the system turned out to be subject to coolant leakage. If not caught in time, the leakage could destroy the processors, logic board, and even corrode the aluminium casing itself. While leakage was sometimes detectable by drops of green coolant in or beneath the machine, in many machines the seepage is so slight that it was almost impossible to detect without dismantling the entire computer. Later models (only the 2.7GHz) were equipped with a Panasonic liquid cooling system which was much more reliable.