Sundowns showed their intentions from the start when Jeremy Brockie nearly found the bottom corner, but shot inches away from goal in the opening minute.
The deadlock was to be broken though on four minutes when Brockie capitalised on a lovely assist from Gaston Sirino for a well-placed finish.
As early from that opener, Themba Zwane nearly added a second but was denied by the upright following a well-timed pass from Lebogang Maboe on eight minutes.
The cruise mode was to be activated when Sirino converted from the penalty spot to hand Downs a comfortable two-goal lead.
Closer to the break, Sirino went close to adding a second but after some lovely footwork from his teammates, missed target from six inches inside the box.
The visitors pulled a goal back four minutes into the second stanza after a lapse in concentration at the back with Seydou Sall firing home from 12-yards out.
Hlompho Kekana restored a two-goal cushion for the Brazilians with a good finish outside the box ten minutes after the break, making it 3-1 on the night and 5-1 on aggregate.
Jose Ali Meza made it 4-1 for the home side in the 61st minute with a simple finish in the centre of the box after Themba Zwane got past his marker to make the pass.
Mosa Lebusa was unlucky not to score for Masandawana six minutes later as his powerful header came crashed against the crossbar.
The Brazilians were in complete control of the match with a quarter of an hour remaining.
Lyle Lakay made it 5-1 eventually for the Brazilians three minutes before time with a simple finish at the near post as the South African champions advanced to the first round of the competition.
Sundowns: Mweene, Ngcongca, Arendse, Lebusa, Lakay, Manyisa, Kekana, Maboe, Zwane, Sirino, Brockie.
Subs: Pieterse, Coetzee, Silva, Morena, Laffor, Meza.