53-year-old Thordarson will be given a contract until the end of the season and an incentive to drag the Railwaymen away from the relegation zone.
The former Stoke City manager has been out of the Englsih game since 2006 when he was sacked at Notts County after the Magpies failed to get into the play-offs.
Gudjon took over as Stoke manager back in 1999 after an Icelandic consortium took over the club during his time up the road in the Potteries he guided them to the Auto Winscreen Shield and promotion to the Championship.