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///M3 Forum
The BMW E46 ///M3 is the M version E46 and puts out an amazing 333 HP and 262 lb-ft of torque at stock specs! There are an amazing amount of modifications for both the coupe and convertible models so read up and get started modifying your cars today!

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Old 03-01-2013, 01:02 PM   #1
Chard
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Loud Metallic Rattle/Clanging Sound...diagnosed

I just wanted to share some info on this in case anyone else is experiencing the same thing.

I was getting a loud metallic banging sound coming from under the car while going over rough roads or bumps. It was extremely loud and sounded like a heavy metal on metal rattle, not a small rattle or squeek.

I didn't know where to start , but I isolated the sound to the rear (I noticed it would only start when the rear wheels were going over bumps). I decided to take the wheels off and bang around with my fists to see if I could replicate the sound. I was able to get a faint replication when I hit the calipers.

So I took them off and it turns out the inner rear brake pads are only held into the piston with 3 prongs. The prongs on my pads must have been bent in too much during installation and were rattling around in the piston...the source of the noise.

The fix? I just bent the prongs back to provide more tension so the pad would hold itself in the piston. Problem solved.

So words of caution: don't bend the prongs back and forth as this can weaken the metal and I'm sure they will eventually break off, leaving you with a useless brake pad. Also, you don't want to bend the prongs TOO far back otherwise you won't be able to get them into the piston.

Anyway, sorry for the lengthy post, but hopefully someone finds this useful if they're trying to diagnose a rattle.
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Old 03-01-2013, 01:14 PM   #2
taylor192
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I've had a rattle for a few months I haven't been able to find. Your post reminded me I changed rear pads a few months ago. Going to check them this weekend, thanks for the post!
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Old 03-01-2013, 01:17 PM   #3
Chard
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Cool, I hope it works out for you. Nothing worse than not being able to diagnose a rattle.

BTW, the sound I was getting was so loud it was embarrassing to drive downtown, where the sound was made even more loud because of the city block echo. But it really depends on how loose your pad is in the piston.
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Old 03-01-2013, 01:26 PM   #4
taylor192
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Quote:
Originally Posted by Chard View Post
Cool, I hope it works out for you. Nothing worse than not being able to diagnose a rattle.

BTW, the sound I was getting was so loud it was embarrassing to drive downtown, where the sound was made even more loud because of the city block echo. But it really depends on how loose your pad is in the piston.
I know! Mine sounds like it is coming from the passenger rear corner of the convertible, although recently I hear it on both sides. Over small bumps there's no rattle, it takes a large bump to jar whatever is loose to make it rattle. Unfortunately I cannot replicate a jarring bump by bouncing the car up/down or side/side while parked.

I have checked everything in that area (vert top, vert storage) then checked the rear suspension (RSM, RTAB, sub-frame, ...) and even emptied the trunk and checked the battery so I've been stumped. Hopefully you have found it!

What brand of pads do you have? I put in Hawk HPS and now that I think about it remember the pads didn't fit perfectly.
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Old 03-01-2013, 01:29 PM   #5
Chard
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I have no idea what pads I have. I just bought the car recently (pre-owned obviously) so I'm trying to figure out all the quirks. The pads fit, but whoever put them in bent the prongs in too far.
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Old 03-04-2013, 09:48 AM   #6
taylor192
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Checked mine this weekend, the prongs aren't the issue, its the pads themselves.

I noticed both sides are too short on the rear inner pad of my Hawk HPS pads. The bottom sits in the guide while the top is ~2mm short of the guide. Thus I can use a screw driver to rock the pad back/forth, which makes a sound similar to the rattle I hear. The outside pad fits perfectly.

Bending the prongs won't help this, the inner pads are just too small. Has anyone else experienced this? Any work around other than ordering oem pads?
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Old 03-04-2013, 06:37 PM   #7
03BIMMERM3
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I think u may have diagonosed my problem, ill have to check my pads..I hear a metal on metal clang also whenever I go over hard bumps..I thought maybe I blew a bushing or my rear suspension was shot (have coilovers)

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Old 03-04-2013, 06:56 PM   #8
BWOODM3
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Sounds like all of this might be my problem as well. I also remember my hawk hp plus pads not fitting correctly (the metal prongs). I'll have to look into this over the weekend
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Old 07-09-2013, 02:05 PM   #9
CPTPowell66
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I finally found a post without all the stupid banter about this issue-thanks! Question for you all-I have same problem and had put new zimmerman z-coat calipers on and pretty sure I used Wagner Thermo-quiet ceramic pads all around to later get the "rattling" sound over bumps. Has anyone else seen this with Wagner-ceramics? Is this a common problem with the 3 prong pads? I will be replacing her right barrel coil spring (not the issue) and checking the inner brake pads. Will get back with findings and resolution to the problem-it is embarassing driving an Ultimate Driving machine with rattle over the bumps! Anyone use any type adhesive or tacky sealeant to help maintain the pads to the piston? Think this would help?
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Old 07-10-2013, 12:10 AM   #10
chrismkay3
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I have this problem, replacing my rear pads is on the list of things to do soon. If I'm going thru all the effort to remove the caliper I may as well put on fresh pads
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Old 07-16-2013, 03:29 PM   #11
Gregy617
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Iv had this exact problem for the longest time.. at first i thought it had something to do with the shock mounts, but I just replaced my rear suspension and its still there...Hopefully this is the fix...everytime I go over bumps its coming from the rear right wheel
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Old 07-17-2013, 11:22 PM   #12
Wordsquirrel
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I spent $6.00 on copper/silicone gasket sealant and it completely fixed it. I applied enough to cover the brake piston where it contacts the inner brake pad. When my car was on terra firma, I drove forward and braked to set the position of the pads and allow the sealant to be compressed. Within 24 hours I drive and the loud metallic rattle at every little bump was utterly absent.

Last edited by Wordsquirrel; 07-17-2013 at 11:24 PM.
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Old 07-17-2013, 11:23 PM   #13
Wordsquirrel
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Permatex® Ultra Copper® was the gunk I used. Wal-mart. I should also add that nothing should get on where the brake pad contacts the rotor.
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