The climax of Dumbreck's 1998 season was victory at the Macau Grand Prix – a race that traditionally attracts entries from all the world's top flight Formula 3 drivers.

In that same year, Dumbreck escaped uninjured from a violent crash during the 1999 24 Hours of Le Mans race when his No.

[2] An aerodynamic design flaw caused the front of the car to rise and then flip without any external contact; Mark Webber had already suffered similar crashes in the No.

6 car was retired immediately, and the team withdrew from all other planned entries in endurance racing and the American Le Mans Series.

In 2015, he won third place overall at the 43rd ADAC Zurich Nürburgring 24 Hour Endurance Race with Falken Motorsports.