The Brazilians created several opportunities at Estadio Nacional de Tundavala in Lubango but could not find a way past the hosts, leaving the contest finely poised ahead of Friday's return leg in Tshwane.
The match started 30 minutes late because of adverse weather and pitch conditions, but Sundowns made a promising start once play got underway.
Brayan Leon nearly opened the scoring inside five minutes after being sent through by Nuno Santos, only for a Wiliete defender to clear his effort off the line.
Teboho Mokoena then tested goalkeeper Beny with a long-range free-kick, while Tashreeq Matthews also threatened as Sundowns looked to take control of the encounter.
However, the visitors suffered a setback shortly before half-time when Mokoena was forced off with an injury following a heavy challenge. Bathusi Aubaas replaced the midfielder.
Sundowns also began the match without captain Ronwen Williams and Aubrey Modiba, who were ruled out with minor injuries. Ricardo Goss started in goal, while Fawaaz Basadien came into the side at left-back.
Wiliete offered more resistance after the interval and forced Goss into important saves, including a close-range effort from Agostinho Cristovao Paciencia Mabululu.
Matthews came close to restoring Sundowns' attacking momentum in the 66th minute, but Beny reacted well to deny him inside the area.
Substitute Iqraam Rayners had another opportunity late on, only to send his effort wide as Wiliete held firm to secure a draw.
Sundowns, who received a bye through the first preliminary round, will now look to capitalise on home advantage in the second leg as they pursue a place in the Champions League group stages.
Mamelodi Sundowns coach Miguel Cardoso wants his side to show aggression and attacking intent against Wiliete SC in the decisive second leg of their CAF Champions League preliminary round tie on Friday.
Mamelodi Sundowns head coach Miguel Cardoso says his side will have to be at their best to overcome Angola's Wiliete SC in the first leg of their CAF Champions League second preliminary round clash on Sunday.
Mamelodi Sundowns coach Miguel Cardoso has admitted that the draw for the CAF Champions League has handed his side a difficult assignment, with Angolan leaders Wiliete S.C. standing between them and a place in the group stages.
Orlando Pirates, Kaizer Chiefs and Mamelodi Sundowns may have avoided each other in the Carling Knockout round of 16, but their respective fixtures present different challenges as they begin their campaigns in the competition.
