I have a Grand L3130 with 110 hours. The 3 point hitch will not lower unless there is substantial weight on it - such as a box blade. The 6' rake is not heavy enough to lower it unless I stand on it for added weight. All fluids are at proper level and routine maintenance has been done. Is there a possibility that I have air in the system? And where would I bleed the system if air may be present?