Mazda3 Forums banner

knocking from rear brakes when cold

5K views 10 replies 4 participants last post by  rrhemi 
#1 ·
My 2004 hatch has an odd noise from the rear, pretty much when cold, and is now much worse because... it's cold out!
The rear rotors were warped, I thought that might be it, so I replaced just the rotors, but the noise continues. it's like "tocka-tocka-tocka-tocka...", but will quiet right down if you press the brake pedal. As soon as you lift, the noise may reappear. It tends to go away after several miles. It can get somewhat louder if you turn left or right.
The new rotors are Wagner (as were the old) that I got off Amazon, so I don't think that's it, besides, the NEW rotors aren't warped! Is it possible that the wire clips on the calipers do not have enough tension? I didn't remove them when I took off the calipers, so I may have bent them too far when removing/replacing the calipers (just a guess on my part...) I don't have any other explanation. But, they don't really LOOK wrong (not obviously bent and not contacting the caliper mount, that would be an obvious thing).
The rear bearings were replaced two years ago at Mazda Bedford (they replaced the bearing AND the hub it was in, saying they don't just press out the bearings any more). So, I don't think it's bearings, and the noise wouldn't stop when the brakes are applied. Any other ideas?
 
#2 ·
You .. bent? the clips? Why'd you do that lol.
Usually those really are for vibration than anything else, I can't imagine they are a cause here (but you should never ever bend them out of shape).

How are the pads, fair shape?

I want to say something is either loose, and not firming up until warm (ei bolt), or the pads are not seating properly which could possibly be an issue of not having good lubrication on the slider pins; until compression of course.
 
#3 ·
I "bent" them out of the way to remove the caliper, rather than remove the springs. That is, I pried them up and over the caliper mount after I loosened the bolts, so I could remove the caliper.
The pads were indeed re-greased where they contact the caliper mount. The pads are in good shape, no more than half-worn. Not sure why the rotors warped in the first place. There may have been an issue with the parking brake cable rusting, so I've stopped using it.
I suppose I could take the wheel off, remove the clips and check that they are not somehow bent so that they gently rest on the caliper mount, but don't actually apply any pressure. That's the best idea I can come up with now.
 
#5 ·
Well, this is odd... I had the tires replaced Saturday (55,000 on 50,000-mile tires) and the sound has gone away! Saturday was the busiest day of their year, they got it done 2 hours after normal closing... I can't imagine they just decided to poke around with something and fix something and not tell me about it! If I were them, I'd put the tires on and be done with it!
They did an alignment, but that doesn't sound like it would make a difference. Another oddity: I replaced Conti ExtremeContac DWS with the same tires, and now the steering feels lighter, quicker, better feel on a dry road... which is the exact opposite that I would expect! The tall rubber blocks would be squishy, versus the near slicks that I was driving around on (OK, they were worn down to the wear bars, not actually slick, but nothing you would want to drive in the snow, or even a heavy rain). Had I changed brands of tires or model, I could accept that one was different from the other. As far as I know, none of the tires had bad belts or anything, I'd never even had a flat. I'm very happy with the way the car feels now, I suppose the alignment might have helped something, but it would have had to have been pretty far out to make such a difference.
Meanwhile, no noise from the rear brakes after the tires were replaced. I have no idea what this means...
 
#6 ·
The noise came back, no surprise...
I have a solution! When I replaced the warped rear rotors in July, I used the old pads, since they still had decent wear (40,000 miles, but the rears don't get much use). Note I said "warped" rotors!
I think what happened is the warped rotors kept moving the pads, which wore down the "tabs" on the mounting pads, that rub against the brake hanger. Well... it must have worn the tabs, because I jacked up the right rear and spun the tire, and could see the pad move up - "click" then down, then up "click"... so I ordered new pads (again, Wagner Thermoquiet). They arrived today, but I came home from work sick, and working in the cold while sick just doesn't seem wise. However, I'm glad it's the pad moving in the brake hanger, at least I know what the issue is finally! The pads are actually quite reasonably priced on Amazon.

http://www.amazon.com/gp/product/B001O0ZLW2/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

The picture is wrong, the actual parts look correct.

Oh, and I checked the clip, removed it (yes, it WAS hard to remove, I live in Ohio with salt on the roads, so the clips were rusted into the aluminum calipers... the fronts I did recently and they weren't much trouble at all!) Anyway, after making sure the clip applied decent pressure, there was no effect on the clicking sound at all. Now that I see what is causing the noise, I know the spring clips have no effect on this.
 
#7 ·
New pads installed last night, no knocking today! I checked the brake pads side to side, the new ones looked maybe a TINY bit taller? AH, but I didn't check the, uh... How do you say this? If you think of the shape like a bracket thus [ , then the INSIDE of the bracket, top to bottom.
Anyway, new pads seemed to have done the trick! The old ones were at least half-worn, but far from "totally gone". Still, I'm happy to have that irksome noise gone!
 
#8 ·
Well, the noise came back! Not as bad, but...

So, I started thinking what could be causing the rhythmic cause of the noise, maybe the rotors were wobbling? They are new in July, so I didn't think they were warped (I suppose it's possible, if I had used the brakes hard). I took the rotor off, and then filed any rust/corrosion off the face of the hub that the rotor mates to. Remember, you guys from fairer climates, that in NE Ohio they put salt on the roads in the winter, so rust is a major issue.
This is my third day driving, no more noise, but I'm now feeling skeptical. I have noticed a slight noise from the read just after the car starts moving, but I don't think I would notice that if I wasn't listening for trouble! It MIGHT be cured, but might not.
The outside pads on BOTH sides appear to be hitting only the outside half of the disk. After just a few days of very mild driving, maybe they just aren't seated yet. I looked, the pads appear to be flat against the disk, and I also filed away any corrosion on the face of the caliper, where the pad mates to the caliper, in case some layer of crud was causing uneven pressure.
Another thought, perhaps unrelated: I have 4 new rotors, new pads, new tires... when I drive at slow speed, I hear a rhytmic noise: rrrr -rrrr-rrrr-rrrr... not anything rubbing, more like tread noise? But, this was true with my old tires, still true with the new ones? They are a month old, certainly not due for rotation. One other clue, the noise decreases when I turn slightly left, increases when I turn slightly right (as if changing lanes, but this is most obvious at lower speeds, 35MPH, when the wind noise doesn't mask the road noise.) Is this normal?
 
#10 ·
No, the spring is in the inside, the non-sprung on the outside.
I swear I hear the same rhythmic knocking last night, but I was too tired from a long day at work to do anything about it.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top