An exhaust valve rocker arm assembly operable in a combustion engine mode and an engine braking mode, the exhaust valve rocker arm assembly comprising: a rocker shaft that defines a pressurized oil supply conduit; a rocker arm that receives the rocker shaft and is configured to rotate around the rocker shaft, the rocker arm having an oil supply passage defined therein; a valve bridge that engages a first exhaust valve and a second exhaust valve; a hydraulic lash adjuster assembly disposed on the rocker arm having a first plunger body movable between a first position and a second position, wherein in the first position, the first plunger body extends rigidly for cooperative engagement with the valve bridge; and an accumulator assembly disposed in the rocker arm and including an accumulator piston that translates within the accumulator piston housing between closed and open positions, the accumulator assembly configured to store a predetermined amount of oil when the first plunger body moves toward the first position, wherein the accumulator assembly further comprises an accumulator spring that biases the accumulator piston toward the closed position, wherein in the closed position, oil is inhibited from entering the accumulator piston housing; wherein in the engine braking mode, pressurized oil is communicated through the pressurized oil supply conduit, through the rocker arm oil supply passage and against an actuator such that the first plunger occupies the first position and acts on the valve bridge during rotation of the rocker arm to a first angle opening the first exhaust valve a predetermined distance while the second exhaust valve remains closed; characterized in that, the accumulator assembly further defines a release hole formed in the rocker arm that fluidly connects with the piston housing, wherein oil is released from the piston housing through the release hole upon the accumulator piston translating a predetermined amount. a rocker shaft that defines a pressurized oil supply conduit; a rocker arm that receives the rocker shaft and is configured to rotate around the rocker shaft, the rocker arm having an oil supply passage defined therein; a valve bridge that engages a first exhaust valve and a second exhaust valve; a hydraulic lash adjuster assembly disposed on the rocker arm having a first plunger body movable between a first position and a second position, wherein in the first position, the first plunger body extends rigidly for cooperative engagement with the valve bridge; and an accumulator assembly disposed in the rocker arm and including an accumulator piston that translates within the accumulator piston housing between closed and open positions, the accumulator assembly configured to store a predetermined amount of oil when the first plunger body moves toward the first position, wherein the accumulator assembly further comprises an accumulator spring that biases the accumulator piston toward the closed position, wherein in the closed position, oil is inhibited from entering the accumulator piston housing; wherein in the engine braking mode, pressurized oil is communicated through the pressurized oil supply conduit, through the rocker arm oil supply passage and against an actuator such that the first plunger occupies the first position and acts on the valve bridge during rotation of the rocker arm to a first angle opening the first exhaust valve a predetermined distance while the second exhaust valve remains closed; characterized in that, the accumulator assembly further defines a release hole formed in the rocker arm that fluidly connects with the piston housing, wherein oil is released from the piston housing through the release hole upon the accumulator piston translating a predetermined amount.