The Bipolars operated on the Coast Division from 1919 to 1953, for most of that period without any serious rebuilding. In 1939 they were renumbered E1-E5. In 1953 all five of the EP-2s, which were 35 years old and worn out from heavy wartime service, were heavily rebuilt by the Milwaukee Road at a cost of about $40,000 per locomotive. The rebuild included additional traction motor shunts for increased speed, roller bearings, multiple unit capability, flash boilers, and streamlining. The E5, rebuilt in the Tacoma Shops as the prototype, performed as advertised, but went over budget, so the Milwaukee Shops were tasked with rebuilding the other four Bipolars. Unfortunately the Milwaukee Shop forces, unaccustomed to working on electric locomotives, did a "poor job" in the opinion of Electrification Department Head Laurence Wylie. (Wylie's successor, T. B. Kirk, stated that he saw a group of disconnected wires in a newly rebuilt EP-2 bundled together and tagged with a written message, "We don't know where these go".) Afterwards the Bipolars were prone to electrical fires and failures, despite repeated attempts by Tacoma Shops to correct them.