The hydraulic system pump responsible for operating the rear brakes is powered by an expensive electric motor. This motor is prone to burnout if it runs continuously. A faulty accumulator ball, located under the hood (bonnet) on the left side near the windshield, can cause the motor to run excessively. The pump should operate for no more than 15 seconds before shutting off. If it continues running beyond this, immediately stop the vehicle to prevent damage to the electric motor, which can cost approximately $1,500 to replace. If you notice the motor running almost continuously, replace the accumulator ball promptly.
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