In June 2000, Valve announced that Team Fortress 2 had been delayed further, attributing this to their rebuilding of the game on a new, proprietary in-house engine that is today known as the Source engine.
Juni 2000 meddelade Vale att Team Fortress 2 hade ytterligare försenats på grund av deras omarbetning av en ny proprietär spelmotor, vilken är idag känd som Source.