Article updated 26/11/12
Sexton, a Londoner who also had spells at Leyton Orient, Chelsea, Queens Park Rangers and Coventry, spent four years at the Old Trafford helm.
He took over in the summer of 1977 and although he didn't win any silverware during his four-year tenure, led the Reds to the 1979 FA Cup final.
Sir Alex Ferguson told MUTV on Monday: "It's very sad news. He's one of the greatest coaches this country has produced. He worked hard at his coaching and tried to improve players technically, spending a lot of time on the training ground. That was his great forte: coaching. Maybe the management position at Manchester United at the time was pretty difficult. But as a coach he was excellent, and as a person, superb. Everyone will have fond memories of him and it's very sad to hear that he's gone."
The Football Association's director of football development Sir Trevor Brooking told the FA website: "It is a sad day for English football.
"Anyone who was ever coached by Dave would be able to tell you what a good man he was, but not only that, what a great coach in particular he was.
"In the last 30 to 40 years Dave's name was up there with any of the top coaches we have produced in England - the likes of Terry Venables, Don Howe and Ron Greenwood. His coaching was revered."