"Today is a difficult day for college football and our Illini famILLy," University of Illinois football head coach Bret Bielema said. "He affected the lives of countless coaches, players, and staff members for more than three decades in college football."
Dimel, originally from Columbus, Ohio, graduated from Kansas State in 1986.
Dimel served as a senior offensive assistant this season at Illinois, following a six-year tenure at UTEP. He is most closely associated with Kansas State, where he was an All-America offensive lineman before beginning his coaching career under Bill Snyder.
He twice served as Kansas State's offensive coordinator, most recently from 2009 to 2017. He spent a total of 20 seasons on Snyder's staffs at Kansas State and was part of 12 bowl teams and the Big 12 championship squad of 2012.
Dimel coached three seasons at both Houston and Wyoming, and went 50-88 overall as an FBS head coach. He also worked as an Arizona assistant from 2006 to 2008.
Illinois hired Dimel in July.
Overall, in his 32 seasons as a head or assistant coach, Dimel mentored 37 players who went on to play in the NFL, according to press release.
Dimel was 62 years old. He is survived by his wife, Julie, and children, Winston and Josey.
ESPN contributed to this report.