Islington-born Sexton was also in charge at Queens Park Rangers and Coventry as well as the England under-21 team, having started out with Leyton Orient.
He led the Blues to FA Cup glory in 1970, and followed that with victory in the European Cup Winners' Cup 12 months later when they beat Real Madrid in the final.
At Loftus Road he led Rangers to their highest-ever finish in the league - runners-up to Liverpool in 1976 - and was in charge of the England under-21s when they won UEFA's European Championship in both 1982 and 1984.
At Old Trafford he reached the FA Cup final in 1979 but was sacked two years later despite United finishing the season with seven straight wins.
During an eight-year playing career he represented five clubs, most notably West Ham United where he made over 70 first-team appearances.
The FA's Director of Football Development, Sir Trevor Brooking, said: "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."
Chelsea legend Ron 'Chopper' Harris said Sexton as the best coach he ever worked with.
"It's a sad day, especially for the players that played under him. He used to spend hours on the training field. He was the best coach I ever worked with. I've got some great memories," he said.
"Dave was a very honest man who would pat you on the back. He came across as a bright lad. You knew when he was upset, you could see it in his face.
"He came from a boxing family and I don't think anyone would have taken him on in the boxing ring."