Sundowns climb to second on the log courtesy of a superior goal difference.
The Brazilians' winner came in the 18th minute courtesy of striker Nyasha Mushekwi who slotted past goalkeeper Jason Barnard for his ninth strike of the campaign in what, strangely, was the home side's only shot on target in the fixture.
With Orlando Pirates - now equal with Sundowns on 50 points - losing to Ajax Cape Town (52 points), the Capetonians top the log after 25 matches.
This bodes well for a thrilling conclusion to the league with fourth-placed Kaizer Chiefs still with a game in hand, and Ajax and Sundowns set to square off next.
For Vasco, their 10th loss of the season means that they remain in 13th place with 27 points with a realistic chance of slipping further down into the relegation zone if they don't string a number of wins together in the last five games of the campaign.
Vasco though, had the first opportunity seconds into the game with midfielder Aidon Jennicker slipping past the defence for his final shot to go narrowly wide of goalkeeper Wayne Sandilands' goal.
Sundowns, who welcomed midfielders Elias Pelembe, Franklin Cale and Matty Pattison into the starting line up, picked themselves up from there to dominate the half.
Striker Katlego Mphela got the first opportunity but shot wide with just Barnard to beat in the sixth minute.
Mphela could have doubled the margin midway through the half when his shot again went wide.
Mushekwi came close to his second before the break with his header going across the face of goal.
Vasco striker Sibusiso Zuma managed to fashion a shot before the interval against the run of play for his effort to be saved by Sandilands.
Sundowns took their foot off the pedal in the second half and let the visitors gain more control even though they failed to capitilise.
Substitute forward Jonathan Armogam had the best chance to equalize after beating a flat-footed Sundowns defence but shot over the post to the dismay of coach Carlos das Neves on the sidelines.
Late chances for Pelembe and substitute forward Mabhuti Khenyeza to double the margin for Sundowns also went wide.