Q: Hear knocking at bottom of engine

Unfortunately, there can be several different reasons that could duplicate the sound of a knock in the engine. With the information provided being limited, it is difficult to determine what the cause of the knock is. In a best case scenario, I would recommend checking the level of the oil, and if it is low, adding the appropriate amount and try starting your Kia Rio to see if the noise persists. If the problem remains, it may be time to enlist the assistance of a certified mechanic to go over your Kia with you. They will be able to diagnose your engine’s knocking noise and perform the necessary repairs to get your vehicle running again.