One problem related to air brake hoses, lines/piping, and fittings has been reported for the 2004 Subaru Impreza. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Subaru Impreza based on all problems reported for the 2004 Impreza.
Metal connector (that is under the car chassis) joining the brake pipes (lines) for the rear brakes rusted through. With the rusted connector, brake fluid leaked through the holes resulting to brakes not to engage and stop the vehicle when the brake pedal is stepped on. Brake pedal would bottomed all the way to floor when it is stepped on. Failure of the brake connector almost resulted into the rear ending of another vehicle. Picture of the rusted connector is available upon request.