It is true that cinder cutting in the draft blower fan was an issue, but the railroad had a regular maintenance program to deal with that. What really did them in was the electrification of the line across the Karoo desert, so there was no longer a need for steam on that section.
The added complexity of the condensing gear, pumps and blower fans were not needed for the rest of the system, so all but a couple of the 25 class locos had the condensing gear removed and the front ends converted to standard 25NC configuration. You can tell these locos by the long, ugly, "sausage" tenders behind them. After the fans, cooling coils and shroud were removed, that is what was left.
3511 was preserved with condensing gear intact, but has not run in at least 15 years. Unfortunately, South Africa has recently cut up a large number of engines that had been held for preservation, so I don't know what 3511's current situation is. I hope someone is able to restore it to service some time in the future. It was an impressive engine.
Michael Allen