You need to specify the order or number which signifies when the Hook gets fired. In this case I beleive it’s 0 and the filter is: wp_admin_bar_render. The action to remove the function I believe is:
remove_action( 'in_admin_header', 'wp_admin_bar_render', 0);
The Function Reference:
Function Reference/remove action
And here it is in the core file: