Wilks was lined up to sign for Carlisle but an approach from Grimsby has taken him to Blundell Park.
United are sending the 19-year-old out for a second time after he returned from a loan with another League Two club, Accrington Stanley, last month.
Wilks played 24 times for Accrington and scored five goals before moving back to Elland Road after playing as a substitute in a 3-0 win against Grimsby on December 30.
United have used him in their Under-23 season during the past fortnight but head coach Thomas Christiansen had no plans to field the youngster in Leeds’ Championship term and Wilks will link up with Russell Slade’s Grimsby before their home game against League Two leaders Luton Town.
Sunderland, meanwhile, have made an enquiry about United’s second-choice goalkeeper Andy Lonergan - signed by Leeds from Wolverhampton Wanderers as recently as August - but the Elland Road club are in no rush to lose Lonergan and will only consider selling him if a replacement becomes available.
Sunderland, whose coach Kit Symons took Lonergan to Fulham from Bolton Wanderers in 2015, are able to offer Lonergan first-team football but his departure would leave Leeds searching for experienced cover for Felix Wiedwald in the last few days of the transfer window.
Liverpool’s Adam Bogdan is understood to be a possible loan option if Lonergan moves on.