1995 Ford Explorer rattling noise when turning

My 1995 ford explorer makes a fast rattling sound when turning at low speeds, usually when pulling into a parking spot. This is an intermittent problem, happening approximately 50% of the time. When it does happen I can turn the wheel to either side and hear the sound. When I press the accelerator and rev the engine the sound goes away completely. The steering system works normally otherwise, it's just an annoying sound.