Amir,
I've always heard the "slight sound of (parking) brake engaging", kind of a soft hydraulic/electronic sound coming from beneath the car when I pull the parking lever. I think it's normal. Have you had any squealing of your brakes at low speed and/or excessive brake dust on your rear wheels? I've had this in the past week or so and came across this bulletin (I believe it pertains to both the Range Rover Sport AND the LR3):
Technical Service Bulletin No.LS206-002
Summary :
A customer may report a concern of a squeal or clicking noise, or of excessive brake dust coming from one or both of the rear brake hubs.
Cause : The electronic parking brake, brake shoe retaining clip has become dislodged or has broken, leading to the above complaint.
Action : Should a customer express concern regarding the above, refer to the Service Procedure detailed in this bulletin.
Parts Required: Parking brake service kit SFS500012
Labour Time: Renew rear parking brake shoes 70.40.09 1.50 hours
Service Instruction
NOTE : In cases where a broken clip has been identified, to ensure a 'right first time' repair, both of the rear brakes should be serviced using the above service kit containing the latest design retaining clip and redesigned brake shoes.
NOTE : The service repair kit should always be used when replacing rear parking brake shoes during routine maintenance, to ensure that the latest specification parts are installed.
CAUTION : Ensure the new retaining clip is correctly positioned into the shoe locating slot.
Renew both rear parking brake shoes using the above parts kit, which includes the modified design shoes, retaining clip and return springs (illustration shows both left-hand and right-hand shoe arrangements and indicates the retaining clip locating slot). For additional information, refer to Global Technical Reference (GTR) Range Rover Sport Workshop Manual Section 206-05, Parking Brake and Actuation - Shoes (70.40.09).