Some Hyundai Elantra owners report experiencing a knocking noise, particularly in cold weather or under load, which is often attributed to piston slap. This issue arises when the pistons do not fit snugly in the cylinder walls and is commonly noticeable during cold start-ups, especially in colder climates. If this knocking sound occurs, some owners may find that it necessitates an engine rebuild or replacement. While piston slap is a frequent cause, other potential sources of engine knocking can include carbon deposits or hydraulic lifters. It is crucial to address this noise promptly to avoid further engine damage, and regular maintenance, such as using the correct fuel octane rating and quality oil, may help alleviate such problems. Consulting a professional mechanic for a thorough diagnosis and appropriate repairs is advisable if this issue arises.

Some Hyundai Elantra owners report experiencing loud knocking noises from the steering wheel, particularly during turns, often accompanied by a jerking motion. Additionally, many owners have faced unexpected loss of power steering assist due to failures in the electronic control system unit, which can lead to significant handling and control issues. Reports indicate widespread problems with the electric power steering, including disabled assist and illuminated power steering warning lights. Although Hyundai does not classify the loss of power steering assist as a safety-related defect in the U.S., it is crucial for owners to address any steering issues immediately, as electronic power steering locking up can pose a serious safety risk, especially when cruise control is engaged. Furthermore, a recall has been issued for certain models due to potential electrical shorts in the Motor Driven Power Steering (MDPS) assembly, which could lead to sudden loss of power steering assist and increase the risk of crashes or injuries.