2003 Chevy Cavalier Rear brake thump, thump, thump

PALEHORSE13

MEMBER
2003 CHEVROLET CAVALIER
4 CYL
FWD
AUTOMATIC
115,000 MILES

I just replaced the rear shoes and drums on my niece's Cavalier. Based on the thiness of the lining on the leading shoe and the fact that the little metal circular clips were still on two of the wheel studs, they may have been original equipment. I used Advance Auto silver series brake shoes and their drums which I believe were new. I reused the brake hardware which appeared to be in good shape. There is not much to the brake hardware on a 2003 Cavalier, and it has a unique horseshoe shaped device that retains both brake shoes. In any case the brake job was very straight forward BUT every time you apply the brakes more than lightly, you hear a thump, thump, thump sound coming from the rear. It sounds to me like it may just be the right rear. I have taken the drums off 10 times and do not see any rubbing, shiny spots, bent parts, hot spots or other abnormal wear. The brakes seem to work fine but the thump, thump thump cant be right (and wasn't there before I replaced the worn out brakes). When I have the car up on jacks with the new brakes installed both drums seem to spin true and feely. I dont see any sign of the parts being out of round.

Wednesday, November 26th, 2008 AT 12:42 AM

4 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Let me try to help here-Did you adjust the brake shoes properly and also turn the drums?

Brake noise in drums is poor contact between the shoes and drum. Heel and toe contact between the shoe and drum is often the culprit, and the cure is to either replace the shoes with new ones or to resurface the drum slightly to increase its inside diameter. New shoes are ground with a slight eccentric to compensate for drum wear. This moves the point of contact away from the ends of the shoes toward the middle. In the old says, mechanics used to arc shoes to match their shape to the drum. But with the concerns about asbestos, shoe grinding is pretty much a thing of the past (though it might make a comeback if and when asbestos is totally out of the picture).

Other causes of drum noise can include weak or loose hardware (replace it), and vibrations between the shoes and the raised pads on the backing plates (apply brake grease).

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Wednesday, November 26th, 2008 AT 1:16 AM

PALEHORSE13

MEMBER
2 POSTS

Thank you for your input but the drums are new and the shoes are rebuilt but new as well. The brake noise is "eccentric" in that it appears to be an irregular rubbing as the brakes are applied and the drums rotate (thump, thump, thump). As I noted in my first post the brakes appear to spin freely and "in true" when up on the jack stands (and no "thump, thump, thump). Whatever the "thump thump, thump" noise is, it only occurs when the brakes are applied fully (no noise when the brakes are applied lightly). I have a lot of "time in grade" with various GM drum brakes (though the hardware/hold down system for these brakes is new to me). I believe the brakes are adjusted properly and I used grease on the backing plate when installing the shoes.

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Wednesday, November 26th, 2008 AT 1:33 AM

RASMATAZ

MECHANIC
75,992 POSTS

Have the drum inside diameter checked with a brake drum gauge-if okay adjust the brake shoe using the same gauge and see what happens.

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Wednesday, November 26th, 2008 AT 2:07 AM

PALEHORSE13

MEMBER
2 POSTS

Thanks for the advice. I will "break" out the old drum gauge and see if using that has the desired effect. I will also replace the hardware. As they are new I may also try swapping the drums to see if the noise "moves" with the drum. Honestly over the sound of that noise she calls music I dont know how she can hear anything. Hopefully I will be getting back to you to report that it is fixed but in the mean time I hope you have a great Thanksgiving.

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Wednesday, November 26th, 2008 AT 8:06 AM