Usually no extra pump
(but depends on distance from engine
to tank). Most often this is caused by an air lock in the secondary loop. There are vacuum tools that are made to remove these bubbles, but the easiest is to make sure there is only one high point in the tubing/piping and put either a manual valve or an automatic air release there and burp air out of the system while the engine
Multiple ups and downs in the hose run make this harder to clear and more likely to occur. Could also be a lack of coolant
in the system, especially if the auxiliary loop is new.