In this study, the effects of different working vacuums on the air flow rate, power consumption, specific energy consumption, pump efficiency and noise level in vacuum pumps of milking machine were investigated. The engine and pump cycles, maximum pump vacuum and oil consumption were also determined in the study. In the study, 4 vacuum pumps with different capacity sizes were used. The air capacities of the vacuum pumps at the pressure of 50 kPa are 600, 1200, 1500 and 2000 L/min respectively in firm basis. These pumps are named VP-1, VP-2, VP-3 and VP-4, respectively. In the experiments, pump vacuums of 42, 44, 46, 48 sand 50 kPa were selected. According to the results of the research, it has been found that the engine and pump cycles and oil consumption values are not affected by different working vacuums, all vacuums have the same cycle numbers and oil consumption. There was no statistically significant difference (P>0.05) between engine speeds and maximum pump vacuum among the four different pumps, but there was statistically significant difference between pump speeds and oil consumption (P<0.05). Within the vacuum pumps, the capacities of VP-2 (1203 L/min) and VP-3 (1570 L/min) specified by the firm at 50 kPa vacuum are maintained. 3% of the capacity of the VP-1 pump, and 13% of the capacity of the VP-4 pump. Except for the VP-4 pump, all pumps consumed power below rated motor power at all operating vacuums. The rated motor power of the VP-4 type pump consumed 16% at 42 kPa and 23% more at 50 kPa. The VP-3 type vacuum pump delivered the highest yield (556.6 L/min kW at 42 kPa and 401.8 L/min kW at 50 kPa) at all operating vacuums. The lowest specific energy consumption was achieved with the pump VP-3 and the highest with the VP-1 type pump. The lowest noise level in the 42-50 kPa vacuum ranges was found on the VP-2 type pump.