When I backing at low speed (especially when down slope), the car can still moving a little bit even I already brake to the deepest position. What is problem? I bought this used car from dealer, the dealer has detail the wheel wall and suspension, so I doubt if it is some detailing spray caused the pad/rotor grease? Does Brake cleaner help in this situation?
And I also worry if air in the brake system. If so how can I tell?

 

Sounds like a brake fluid problem. Bleed the brake fluids and replace with fresh Honda DOT 3. Also check condition of rotors and pads.

 

Thanks. I will do it this weekend. Also I feel hard brake pedal at the end of travel. Is that normal?

 

Are you also hearing/feeling metal on metal when you "feel hard brake pedal"? This would indicate your brake pads are toast, and need to be replaced.

 

metal on metal, en...I dont think so. Maybe I should let brake shop to check it first. Thanks