Themba Zwane returned to home side’s line-up from the first-leg along with Andile Jali, but Ahly dropped Taher Mohamed and started Salah Mohsen up front.
Sundowns’ quest to stage a turnaround suffered a blow on 11 minutes as an un-marked Yasser Ibrahim headed into the net from the game’s first corner-kick.
The first shot in anger from the host followed 20 minutes in through Sphelele Mkhulise, but he went into the empty stands of the stadium from a strike outside the six-yard area.
Masandawana pulled level from a corner on the half-hour mark when Mosa Lebusa rose in the area to send Aubrey Modiba’s delivery past goalkeeper Mohamed El-Shenawy.
Zwane was brought into play for the first time in the game seven minutes before halftime as he dragged one-two from outside the area narrowly past El-Shenawy’s net.
The Brazilians pulled out strong for the second half as a Modiba threatened the lead from a free-kick in a dangerous area outside the box but he went over.
This followed a palm 53 minutes in from El-Shenawy off a cutback at the back-post by Mauricio Affonso shortly after his and Khuliso Mudau’s introduction off the substitutes bench.
Sundowns looked to have gone ahead from a well-taken strike in the area by Peter Shalulile, but it was disallowed midway in the second half after he was deemed to have used a hand in the build-up.
The Tshwane giants didn’t stop pressurizing the Egyptians towards fulltime, as Lyle Lakay and Gift Motupa threatened from two close-range efforts.
However, the Cairo Red Devils soaked up everything thrown at them to progress to the semi-finals of the Champions League.
Sundowns: D.Onyango, Nascimento, Lebusa, Coetzee, Morena, Modiba, Jali, Mkhulise, Zwane, Sirino, Shalulile.
Subs: Mweene, B. Onyango, Lakay, Affonso, Erasmus, Motupa, Maboe, Mudau, Mkhuma
