Decoupler in a hydraulic engine mount (HEM) acts as a binary gate, an ON/OFF switch. Depending on operating condition it either floats or sinks. This study was focused on studying decoupler as a gradual gate rather than binary sub-system. Major objectives of this study involved designing decoupler for a tunable and optimum stiffness response that could deliver desired low and high frequency dynamic response for HEM as a system. A simplified lumped parameter dynamic model was developed for HEM, capable of predicting low and high frequency resonance. Measured characteristics of decoupler and physical linear/non-linear parameters of rubber element along with fluid column were utilized to provide quantitative validation of experimental dynamic response of HEM as a system. Preliminary work shows highly encouraging correlation between analytical model and experimental data. Completion of this study would provide a novel design tool to engineers in successfully handling noise, vibration issue in modern cars.