In this paper, we observed that the enhancement of forced convective heat transfer rate of aluminium automobile radiator after using Al2O3 nano fluid with ethylene glycol base fluid coolant. In this experimental investigation , we consider volume fraction and the flow rate of coolant as parameters. we take volume concentration of Al2O3 nanoparticles in the range of 0.01 to 0.12 % and base fluid is 15 liters. We have chosen sonication process to mix Al2O3 nanoparticle with water using ultrasonic sonicator for 2 hours for getting stable suspension in water. Heat transfer rate were increased by increasing the volume concentration and flow rate .we observed that Maximum heat transfer rate occurred at 0.08% volume concentration i.e. 45 % higher compared to water. After increasing the volume concentration heat transfer rate is just increased compare with previous heat transfer values values. The coolant flow rate is varied from 3 lpm to 15 lpm.