It was caused after a water main burst on Harborne lane in Selly Oak on Thursday.
Thousands of gallons of water flooded the carriageway, trapping cars and damaging about 10 homes.
Part of the road remains closed and Severn Trent said engineers were on site investigating what caused the pipe to burst and how best to fix it.
Ground penetrating radar has been used to help establish the extent of damage and major work is due to start on Monday.
A spokesperson for the firm said it was a "big job" as the pipe was 10m below ground and it was difficult to precisely predict how long it would take to repair.
Local resident Mel Rejayee was one of those to become stuck in the floodwater in her car, an experience she described as "quite scary".
A sinkhole in Birmingham could take several weeks to repair, water firm Severn Trent has said.