Neither the mayor nor any of the members of the council or committees of the council shall direct or dictate the appointment of any person to or his removal from office by the manager or any of his subordinates. Except for the purposes of inquiring or receiving information or advice, the mayor and council and the several members thereof shall deal with the administrative services solely through the manager and neither the mayor nor any member of the council shall give orders to any subordinate of the city. The city council shall have the power to investigate any part of the city government and for that purpose to compel the attendance of witnesses and the production of documents and other evidence.