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Shocks or brakes?

Maintenance/Repairs
#1

I have a 2004 Mazda 3 with 90K miles. Brakes, rotors, and rear calipers were replaced about two months ago. About a month after, I started noticing a clattering sound coming from the left rear wheel whenever I drove over rough road. (It sounds like an aluminum pot lid dropping onto the pot.) The shop that did the original brake work took 4 visits to get everything done. Instead of going back, I went to another mechanic who said the left caliper was loose. He showed me how he could shake it. He said the bolts were tight so it wasn’t a safety issue.

I went back to the original shop for repair but they could not reproduce the noise and said the brakes/calipers were fine.

The noise remained. I went to a third shop which checked the caliper and said it was fine, but said that I needed new shocks. The mechanic had the car on the lift and was able to reproduce a similar noise on both rear wheels when he hit them with a rubber mallet.

The first mechanic insists the caliper is bad. The second insists it’s the shocks.

Any thoughts? Who do I trust?

#2

Were either mechanic at a quick oil change type place?

#3

The original shocks/brakes/calipers was a Mr. Tire. The place that recommended shocks was another Mr Tire with a manager I used for several years when he was closer to me. He was always straight forward and never seemed eager to up the bill. There was a reason I went to him. ; ) He’d keep me up to date on things that needed immediate work and things that would need attention down the road. Other times, he’d make some small adjustments on the car for no charge. (This was all when he worked under “Craven.”)

The mechanic who spotted the “loose” caliper was an independent.

#4

There are two set of bolts holding the caliper on. One set is actually holding the caliper frame on and it should not shake. The other two bolts that hold teh caliper to the frame are actually bushings, often called caliper pins. They should be tight, but the caliper should be able to slide on them. Sounds like the brakes are fine.

#5

That does not guarantee that the shocks are the problem though. They could be but from your description of the last mechanic’s technique, I could not be sure. It could be the shock mounts as these are more likely to make the kind of sound you describe than the shocks would.

#6

Thanks, Keith. That is helpful. I did notice this weekend that the pin on the outside part of the caliper sits pretty tightly against the caliper on 3 of my 4 wheels. On the rear left, I can move the pin significantly. I haven’t tried, but it’s very likely I could slip it off without much pressure. I will be returning to the second Mr. Tire to get that replaced. I will also suggest they look at the shock mounts.

One question: the shock mounts - I assume they can wear out over time though I never had this problem before and keep my cars for decades. To replace brakes, rotors and calipers, could the mechanic have interfered with the shock mount?

#7

Short answer, no. The main issue with strut mounts is the rubber, it will eventually crack and break. Right now, I’d say it is unlikely that the strut mount is bad as your car is too new for this. It could happen, but not likely for another 10 years or so. I just threw that out as a possibility.

#8

I am a little confused and concerned about this pin on the outside of your caliper. This is not the bushing that I was talking about, I can only guess that it is part of the parking brake mechanism. Only that would not be on the front calipers. But if it moves on one wheel and not on the others, it needs to be addressed.

#9

Are the pins you are talking about actually the retaining clip shown in the first picture at this url?

http://autodiyonline.com/mazda-diys/mazda-3-diys/mazda-3-2004-2009-rear-brake-pad-replacement-diy/

#10

I’m concerend that you’re going to Mr. Tire shops for chassis work, especially after the first such shop screwed up the job. I looked at their website, and while they list “over 800 locations” their breath of expertise seems to be all over the map.

The rubber mallet trick may work IF it’s tied to further analysis, like somehow isolating the sound source with a linear accelerometer or even a stethoscope. I’d have to see it to comment.

With great respct to Keith, I’d have to point out that the car is 8 years old, and if you drive routinely on poor roads it could be a strut mount. “Work stress” can effect elastomers as much as time can.

Personally, I’d suggest finding a reputable independantly owned and operated shop and let them look at it.

#11

Could easily be the brake pad chattering up and down within the caliper. Depending on the anti-rattle mechanism for this vehicle. A missing anti-rattle clip produced the same sound you describe in my Subaru. When I went over a bump you would hear the pad rattle up and down within the caliper.

Do this… As you go over bumps and hear the chatter, slightly depress the brakes and see if the rattle is eliminated. That would at least rule out the suspension.

#12

Thank you all for your thoughtful comments! The short and (should be) final version is this: I went back to the second Mr Tire because I had faith in the manager who used to manage a private place near my house. They tried a new shock and when that didn’t work, replaced the old one and took a closer look at the caliper. (Yes, Keith, it was the retaining clip I was referring to up top, but that turned out to be okay.) I think Nebin got it correctly because there’s a second clip on the back of the calipers. That looked fine and everything was in place, but the mechanic was certain the noise was from the caliper and concluded that the caliper was not holding the pad firmly and this was causing the clatter. This confirmed the independent mechanic’s assessment. They’ve ordered a new one to replace the old and there’s no charge.