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Q: rattling noise in rear when driving over even small bumps - what could it be on 2007 Volvo S40

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rattling noise in rear when driving over even small bumps - what could it be - I thought it might be a loose muffler but it appears fine -I can't even jiggle it. The rattle noise has gotten louder over the last 2 weeks. Could this be damagerous?
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you should have a good local Volvo specialist check this noise. yes, it could be dangerous.
I just bought a used S40 that also has rattles in the rear, coming from inside the wheels. A pre-purchase inspection revealed that the caliper slide pins had not been properly lubricated when the brakes were last replaced. This caused the calipers to pull unevenly, wearing out one brake pad faster than the other, and also wearing them at an angle. When the brakes aren't applied, the pad itself (on both sides) is rattling over small bumps. If I apply the brakes over the same bumps, it goes away, confirming what the mechinc identified. Have new Hawk HPS pads on order from If you haven't tried them, they're the greatest for more stopping power without adding more wear to rotors.

Good luck.
Here's a little followup on the rattle noise that I was experiencing. I took it in to be looked at and the garage told me that the anti rattle clip had been broken off ( that's why the noise stopped when the brakes were applied) when the brake pads were installed and that it needed to be replaced along with new brake pads. Since the brake pads had been done within the last month I called that garage and explained the situation - they offered to evaluate and fix. Upon inspection, they discovered the brake pads had been installed incorrectly - appears the Volvo S40 has inner and outer pads and they had installed 2 inners and 2 outers together instead of an inner and an outer...they reinstalled them and they are working perfectly and the sound is totally gone!!!!!!
I was having trouble diagnosing the clunking noise coming from my wife's 2006 S40 and this post led me right to the problem. It's more likely that the outer pads were installed on the inside rather than an outer and outer put together on one side. The back of the inner pads have a blank space where the brake piston applies pressure- the outer pads have little rivits in that same location. If outer pads are installed on the inside, the brake piston will press against these rivits causing uneven pressure, causing uneven wear, which eventually causes noise as the unevenly warn pads wiggles around when you go over bumps. It would be very easy to install the pads incorrectly as they are almost identical in shape and appearance and can be installed in the incorrect position (Volvo really messed up there). The inner pad will usually have the anti-rattle clip attached to it. If this was your issue, be sure to buy new pads and check that the incorrectly installed pads didn't cut a groove in to your rotor. Thanks for this post, it really helped!
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