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  #1  
Old 01-13-2012, 10:20 PM
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Rear Brake Makes Loud Thump when Released.

I have a 2008 Cobalt LS automatic. When I release the brake pedal there is a very loud "thump" noise from the rear end of the car. The car slows perfectly and there is no noise while accelerating, slowing down, or stopping. Only when releasing the brake from a stand-still.

As silly as it sounds, along with the noise it feels like there is a small "bounce" in the rear when I let off the brake pedal. Also, it is much more frequent/noticeable when it is wet/raining.

I have yet to check anything. Thought I might get some ideas first, and see if anyone else has had a similar problem.

Any ideas as to the problem would be appreciated?
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Old 01-14-2012, 06:15 AM
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Is it drum brakes? What kind of mileage? You have described all the symptoms of a drum brake self-adjuster malfunction. Drum brakes are designed to self adjust while braking in reverse, but most people don't brake very hard while backing-up so the starwheel adjuster seizes. I have taken the habit of braking hard in reverse once in a while just to keep brakes adjusted and free. Find yourself an empty parking lot and try it 3 or 4 times or .....You just need a rear brake service to loosen adjuster and adjust brake shoes. What you are experiencing is typical when the shoes are adjusted too far from drum. Here are a few pictures to help understand. Starwheel adjuster is at bottom of drum
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Rear Brake Makes Loud Thump when Released.-drum_brake.jpg   Rear Brake Makes Loud Thump when Released.-brake_duo_servo.jpg   Rear Brake Makes Loud Thump when Released.-brakes.jpg  
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Last edited by Coby7; 01-14-2012 at 09:36 AM.
  #3  
Old 01-14-2012, 11:42 AM
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Thank you very much for the help. I'll take your advice and try braking hard in reverse a few times. Otherwise I'll look into how the rear brakes are adjusted.

Again, thank you.
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