There are two factors for heavy direction: one is that steering system mechanical part of front axle and the other is steering hydraulic assist system. Steering column is lack of oil, which is the main cause for heavy steering caused by mechanical part. The steering column is not maintained for a long term, lubricating grease is not filled in the steering shaft, therefore, master pin and bushing is dry grinding. As a result, steering resistance is increased or even master pin and bushing are fritted. Therefore, during the maintenance, please fill lubricating grease in the steering column. Generally speaking, please lift the I beam of front axle, fill oil in grease fitting installed on camshaft seat with grease gun until I beam and upper and lower surfaces of pinhole can extrude oil.