The Argentine side, who beat Cruzeiro in the 2009 final to lift their fourth title, are second in Group Seven three points behind the Brazilians who beat Guarani of Paraguay 2-0 in Asuncion.
With just one match to go, Tolima have five points and Guarani none.
Estudiantes, knowing a draw would be enough to see them through, took the lead in the 23rd minute when lanky back Federico Fernandez leapt above the Tolima defence to head in Leandro Benitez's left cross.
The Colombian side equalised eight minutes later when Estudiantes defender Nelson Benitez handled the ball and Felix Noguera converted the penalty.
"In the build-up we saw it as a difficult match and it was. We started well, then through our own mistakes and their improvement it got complicated, but we ended up having a good match," Estudiantes defender Leandro Desabato told reporters.
Favourites Cruzeiro, who have been crowned South American champions twice and had already virtually booked their place among the last 16, took their tally to 17 goals in five matches.
Striker Thiago Ribeiro put Cruzeiro ahead early on and their Paraguayan substitute Jose Ortigoza added the second in the final minute.
HOLDERS WIN
In a tight three-way race for two last-16 berths in Group Six, holders Internacional crushed Wilstermann of Bolivia 3-0 at home to put one foot in the knockout phase.
The Brazilian side, with 10 points, opened a three-point lead in the group standings over second-placed Emelec of Ecuador after the teams have played four matches. Chiapas of Mexico are third with six points while Wilstermann have none.
Midfielder Oscar had a brilliant game putting Inter ahead after 18 minutes in a first half which the home side could have ended five goals up against a side they beat 4-1 two weeks ago.
Argentine Andres D'Alessandro increased Inter's lead 12 minutes into the second half with a fine shot inside the box from Oscar's pass.
Ze Roberto hit the third in the 72nd, four minutes after Wilstermann midfielder Lucas Fernandez was sent off for a tackle from behind on D'Alessandro, his second yellow card offence
