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Scraping rattling sound - I thought it was brakes but only does it when hot.

Clint Beastwood

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#1
Yes I am noise obsessed, but anything that is "outside of normal" is wont to draw my attention. This car's fairly quiet, but it does make some really unique sounds that I was not expecting (the DI engine sounds almost diesel-y at idle).
It's going to require a bit of volume and probably headphones - it sounds almost like light knock, but it does not correlate to engine rpm at all and only occurs when stopping.
I did not originally think brakes because I haven't been hearing any squealing, but I just read in a post here that our stock pads don't have tattlers on them, so there won't be a squeal to tell me they're tapped out.

https://youtu.be/KH-AGexvMgg between 0:06-0:09, that rattling sound behind the road noise. It does get louder at some times, but not enough that I can reproduce it easily.

For a while I was worried it was engine related, but since the car runs flawlessly otherwise and I cannot reproduce the sound with it sitting statically, I do not believe so.
I have ordered rotors and front pads anyways because I'll need to replace them eventually. I've exercised my split-half troubleshooting methodology to eliminate variables and come up with consistent "steps to reproduce", outlined below.
I gathered data from 47 trips in the car spread across 22 days, refined into the below dataset. I suppose it *could* be my front pads are gone, but if so its the oddest brake grinding I have ever heard, and its crazy quiet for grinding brakes. It's more of a tapping or light knocking than a scrape, but I've been wrong before.

Variables
1. Only at temperatures above 65f.
2. The car must be up to temperature, does not do it when completely cold.


Steps to reproduce
- Be driving, roll to a stop.

Induced variables
\ In gear or out of gear, does not matter.
\ Clutch in, clutch out, does not matter.
\ Does not relate in any way to engine RPM.
\ Does not occur under hard braking.
\ Does occur if I stop on a downhill, let the car get up to speed via gravity only and come to a gentle stop. Did not test with engine off though.
\ I do not feel it through the clutch or brake pedal, but I do kinda feel it through the steering wheel. I do not feel any "pulsing" like I would with a warped rotor.


Have also noticed
\ Car occasionally makes a snapping or sharp banging sound when backing up a hill (driveway) as the weight transfers during clutch engagement.
\ It has been getting slowly louder.
\ It was much louder when I had my Cobb RMM installed.
\ Rotors do not appear to be grooved at all, though there is a bit of a lip on the outside edge.
\ Crappy mileage; ~21mpg.

I'm going to try to swap pads and rotors this weekend if my pads from whoosh get here in time, otherwise I might just go grab some stock pads at the dealer to get it done.
 


Last edited:

alexrex20

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#2
Brake pads are metal on metal. The pad frame is beginning to scrape on the lip of the rotor. It's intermittent because lip will wear down as it rubs against the pad frame.

Pulling the wheels off and looking at inner and outer pads is the only way to verify pad life.

Sent from my SM-G960U using Tapatalk
 


OP
Clint Beastwood

Clint Beastwood

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Thread Starter #3
Brake pads are metal on metal. The pad frame is beginning to scrape on the lip of the rotor. It's intermittent because lip will wear down as it rubs against the pad frame.

Pulling the wheels off and looking at inner and outer pads is the only way to verify pad life.

Sent from my SM-G960U using Tapatalk
Oof 15k on a set of pads!

I haven't had the wheels off yet, that's tomorrow :p waiting on another set of jackstands, mine are under another project.
 


RubenZZZ

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#4
Brake pads are metal on metal. The pad frame is beginning to scrape on the lip of the rotor. It's intermittent because lip will wear down as it rubs against the pad frame.

Pulling the wheels off and looking at inner and outer pads is the only way to verify pad life.

Sent from my SM-G960U using Tapatalk
This.

I bet the inside pad is worn thru in one corner.

My car tends to do that. Sometimes it grinds and then it stops grinding. Since the pads dont have tattlers and the outside pads look good you won't know.

Its happened twice to me.

Sent from my LGLS992 using Tapatalk
 


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Clint Beastwood

Clint Beastwood

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Thread Starter #5
This.

I bet the inside pad is worn thru in one corner.

My car tends to do that. Sometimes it grinds and then it stops grinding. Since the pads dont have tattlers and the outside pads look good you won't know.

Its happened twice to me.

Sent from my LGLS992 using Tapatalk
THANK YOU I was poking the outside pad with my finger and it felt low but not gone, can't reach the inside one but it does make sense.
I ordered some EBC from whoosh but they won't be here until next week, I think I'm going to grab some stockers and slap those on tomorrow, then go to the EBC's next change.

Always having squealers, or more recently pad sensors, had made me lazy about checking such things. Lesson learned (and probably forgotten soon lol).
 


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Clint Beastwood

Clint Beastwood

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Replaced pads and rotors. Stock pads still had ~30% left at 15k miles. EBC pads from Whoosh didn't get delivered so I grabbed some stock pads - they're supposed to be the same but they feel really "wooden". Whomever said the inside pads wear faster was totally right. No indication of the pad rubbing against the rotor anywhere. I didn't have a 17mm that was thin enough so I had to thin one down on the grinder and polish it back up.

The grinding/whirring sound is still occurring when coming to a stop :| If this makes sense, it seems like it relates to the DMF noise when engaging throttle after coasting, it doesn't do it at idle or revving, only as the car is rolling to a stop. The wheels spun freely with the car off the ground so it didn't feel like brake binding, and the wheel bearings looked adequately lubricated.
 


JDG

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#7
Replaced pads and rotors. Stock pads still had ~30% left at 15k miles. EBC pads from Whoosh didn't get delivered so I grabbed some stock pads - they're supposed to be the same but they feel really "wooden". Whomever said the inside pads wear faster was totally right. No indication of the pad rubbing against the rotor anywhere. I didn't have a 17mm that was thin enough so I had to thin one down on the grinder and polish it back up.

The grinding/whirring sound is still occurring when coming to a stop :| If this makes sense, it seems like it relates to the DMF noise when engaging throttle after coasting, it doesn't do it at idle or revving, only as the car is rolling to a stop. The wheels spun freely with the car off the ground so it didn't feel like brake binding, and the wheel bearings looked adequately lubricated.
It sounds like maybe a CV joint failing in the axle. I may be having a similar problem but it presents itself during right turns.
 


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Clint Beastwood

Clint Beastwood

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It sounds like maybe a CV joint failing in the axle. I may be having a similar problem but it presents itself during right turns.
Argh I guess I am going to *have* to go to the dealership :|
 


JDG

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Only 15k miles. I am essentially one-handed though, so most things take me 10x as long.
Assuming you don't have modifications that would disqualify you, take it to the dealer to get their thoughts on the noise. That's pretty low miles for a CV to go..
 


dmb

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don't forget to close up the box after you open it to look at those pads they[ebc red] stink. and if you do the rears don't forget to screw in the parking brake puck counter clock wise R/S and clock wise L/S. I removed the backing plates so i could view the rotors. all they do is stop the view and retain the heat, i see no ice ever, not that i'm fast enough to make a difference.
 


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Clint Beastwood

Clint Beastwood

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Thread Starter #13
don't forget to close up the box after you open it to look at those pads they[ebc red] stink. and if you do the rears don't forget to screw in the parking brake puck counter clock wise R/S and clock wise L/S. I removed the backing plates so i could view the rotors. all they do is stop the view and retain the heat, i see no ice ever, not that i'm fast enough to make a difference.
i am fighting the urge to go smell the brakepads now :p
 


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Clint Beastwood

Clint Beastwood

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It sounds like maybe a CV joint failing in the axle. I may be having a similar problem but it presents itself during right turns.
Think you might be right. I went into a big open parking lot and did full-lock 360 turns. There's a substantial popping that I can feel through the wheel in exactly the same part of a full-lock left turn, doesn't happen on a full lock right turn.
 


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JDG

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Think you might be right. I went into a big open parking lot and did full-lock 360 turns. There's a substantial popping that I can feel through the wheel in exactly the same part of a full-lock left turn, doesn't happen on a full lock right turn.
Yeah this is exactly what mine is doing. It is not quite a "pop" yet just a bit of a rattle noise. It isn't really bad yet and since my plan is to replace both axles anyway when I install my LSD, I am going to wait until they get worse. I am just surprised yours are gone at such low mileage. Can you see any rip in the boots or grease slung up around the axles?
 


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Clint Beastwood

Clint Beastwood

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Yeah this is exactly what mine is doing. It is not quite a "pop" yet just a bit of a rattle noise. It isn't really bad yet and since my plan is to replace both axles anyway when I install my LSD, I am going to wait until they get worse. I am just surprised yours are gone at such low mileage. Can you see any rip in the boots or grease slung up around the axles?
No external indication. I have had an RMM on for ~10k miles, and I started noticing this noise around the time I installed my first RMM. I originally chalked it up as a normal noise from the car I just had never noticed, but as its grown louder it has concerned me more. I removed my RMM and it got much quieter, but it's still there. Only when hot though, which I thought was weird.
 


JDG

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No external indication. I have had an RMM on for ~10k miles, and I started noticing this noise around the time I installed my first RMM. I originally chalked it up as a normal noise from the car I just had never noticed, but as its grown louder it has concerned me more. I removed my RMM and it got much quieter, but it's still there. Only when hot though, which I thought was weird.
Have you inspected you driver and passenger engine mounts? I wonder if one of those have failed?
 


kivnul

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... and if you do the rears don't forget to screw in the parking brake puck counter clock wise R/S and clock wise L/S. ...
Bit of a thread jack but for both my rears it is clock wise. I think both calipers are identical.
 


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Clint Beastwood

Clint Beastwood

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Have you inspected you driver and passenger engine mounts? I wonder if one of those have failed?
Driver's side looked ok, the passenger one makes a squeaky sound if I move the engine with my hand and in the morning when it's cold. Now that I have the exact criteria required to replicate the issue I can take it to the dealership and provide them an exact "do exactly this to replicate the grinding". I find dealerships are less error-prone when I provide such.
 




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