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Brake pad wear indicator sound? or something else?

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Old 11-07-2018, 10:51 AM
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afrayedknot
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Brake pad wear indicator sound? or something else?

I recently started hearing a metal on metal grinding/rubbing sound when I brake, most noticeably during the beginning of the drive. It sounds like it is only coming from the passenger side. I first noticed it last week when I was leaving the garage at work. Sounded like metal rubbing on metal and then a loose metal arm catching on something. I thought it was the brake pad wear indicator so I immediately ordered a set of new pads, which will be arriving today. However, the sound isn't consistent and sometimes I can hear it when I haven't depressed the brake lever.


This morning it was very loud when I left for work and while the sound continued, it softened the further I drove. And at times I noticed that it didn't make any noise when I brake to a stop. Is this how the brake pad wear indicators normally function? or is there another issue I should look into? I read a post on the forums about someone having a problem with their parking brake catching and rubbing against something, but I am unable to locate that thread. (edit: found the link, but after reading over it again, I am not experiencing the same clicking sound) https://www.myg37.com/forums/g37-cou...ing-brake.html


This is a g37x sedan with 41k miles. The last 20k miles were primarily city driving. I do not believe the brake pads have been changed since the car was new. I bought it used at 21k miles.


I have a sound clip from my dashcam and will upload that as soon as I get home from work.

Last edited by afrayedknot; 11-07-2018 at 11:32 AM. Reason: Link
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Old 11-07-2018, 01:22 PM
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Jsolo
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Many of us get this after the car has been sitting over night. Backing out of the garage it makes a squealing sound of sorts. No other noises for the rest of the day. Pads have plenty of material left.

If it were me, I'd pull the wheels off and inspect the pads in each caliper. You'll see right away how much material is left on the inbound & outboard pads. Replace if needed. If there's uneven wear, make sure caliper sliders are well cleaned and lubricated when assembling. Always do brakes as an axle.
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Old 11-07-2018, 02:01 PM
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Could be the dust shield rubbing. Mine got pulled on at some point during a wash and was rubbing against something behind the rotor. Had a metal on metal like sound. I thought it was brakes at first but I pushed it away and the sound went away.
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Old 11-07-2018, 03:05 PM
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I addition to whats been mentioned above, it could also be a sticking caliper on one side causing one pad to be worn off prematurely...look at the discs and see if there are any grooves on the disc on the side making noise that don't appear on the disc on the quiet side this may be a preliminary sign of a sticking caliper but when you have the old pads off compare the two and see if one side is significantly more worn than the other ...thats a more definite sign the caliper is sticking....

at your mileage needing new pads sounds reasonable so if the pad wear is even just changing the pads should do the trick
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Old 11-07-2018, 09:41 PM
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Thanks for the suggestions. I'll be sure to keep those in mind during the replacement. After some more reading and youtube videos, I am fairly certain that it is the wear indicator rubbing, but will remove the wheel to inspect for sure. I put air into my tires the other day and forgot to plug the dash charger back in, so unfortunately I do not have a video of the sound.
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Old 11-11-2018, 10:51 PM
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Just got my rear brake pads replaced today and that got rid of the squeak. However, I also had my mechanic flush the brake fluid. On my drive home I stopped at a red light with my foot firmly on the pedal. I noticed that if I applied more pressure the pedal would continue to depress all the way to the floor. I let go and fully depressed it a few times and I could hear a whooshing sound of air from the master cylinder area.

My question - is this a normal occurrence after a brake fluid flush that will go away on it's own? Or did my mechanic not do a proper flush? I don't think I've ever tried to further depress the brake pedal after I've come to a full stop, so I am not sure if this was the case before I had the brake fluid flushed.
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Old 11-12-2018, 12:40 AM
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Went for another drive and something is definitely not right. It feels like there is a air leak within the system. When I come to a full stop with slight pressure on the brake, it will continue to depress/sink. If I apply even more pressure I think it will bottom out. And when I let off, but not enough to allow the car to move, and pump the brakes I can hear hissing coming from the master cylinder area. Does this sound like a damaged seal in the master cylinder during the bleeding process?

The car was bled the manual method way with me pumping the brakes as he opened/closed the bleed valve.

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Old 11-12-2018, 10:27 AM
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that doesn't sound right, I would check the level in the MC it might be a bit low, but if you're not getting any codes its probably not too bad most likely, it might it might not have been bled properly and just needs to be bled some more.
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Old 11-12-2018, 11:22 AM
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Fluid level in the MC is at max. No error codes or warning lights. The brakes work and stop as they normally would, it's just the pressure doesn't hold when I pump the brakes while stopped with engine running.

I was reading the procedure for manually bleeding brakes with two people, one pumping the brakes and found out that the brake pedal should not be fully depressed to the floor during the bleeding process. I was not aware of this when I was doing the pumping and each time we bled the valve I depressed the pedal all the way to the floor and held for 2-3 seconds, while he closed the valve, before letting off. Is it possible that fully depressing the pedal during bleeding has caused this issue?

I do not think it is a problem with the brake booster since the pressure gets firm and holds when I pump the brakes after I turn the engine off. However, I am going to recheck it during my lunch break following these steps I found online to rule it out for sure.

Power Brake Booster Test 1
1. With the engine off, pump the brake pedal to remove any residual vacuum in the booster.
2. Hold pressure on the pedal while you start the engine. When the engine starts, the pedal should drop about a 1/4″, this indicates that the booster is working properly.

Power Brake Booster Test 2
1. Run the engine a couple of minutes.
2. Turn the engine off and press the pedal several times slowly. The first pump should be fairly low. The second and third should become slightly firmer. This indicates an airtight booster.

Power Brake Booster Test 3
Start the engine and press the brake pedal, then stop the engine with the pedal still pressed. If the pedal does not drop after holding the pressure on the pedal for 30 seconds, the booster is airtight.
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Old 11-12-2018, 11:54 AM
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I always put a piece of 2 x 4 under my brake pedal when doing it manually. You can pick up a cheap reverse bleeder and avoid this problem all together. Also, allows you to do it by yourself.
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Old 11-12-2018, 12:36 PM
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Thanks, as soon as I rule out the possibility of problems with the booster, MC, or hoses, I am going to pick up a pneumatic brake bleeder from harbor freight and re-bleed the system. Hopefully it's just some air in the system.
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Old 11-12-2018, 12:42 PM
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I'm a fan of the motive power bleeder for this car. It's a only man operation. Works well, gets the job done without possibly damaging the MC by bottoming it out. Not that bottoming it out should cause damage, but consider this. During typical braking, mc piston travels a certain amount. When bleeding as described above, you're forcing the mc piston to travel beyond this point which may have a rougher surface or have other debris, causing more wear in the piston seals resulting in internal mc leakage (pedal not able to hold pressure).

Simple test is pump up the pedal with the car off and hold. If it doesn't sink after a period of time then mc seals should be good.
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Old 11-12-2018, 02:38 PM
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I saw the motive bleeder and was intending to purchase that, but I found a thread (https://g35driver.com/forums/g35-cou...eder-kits.html) that mentioned the bleeder from Harbor Freight is not only cheaper but works much better than the motive. I think I just need to purchase an air tank.. So that's the reasoning behind me considering the Harbor freight over the Motive.

So I went out to my car during my break. While the car was off, I pumped the brakes 3-4 times and each consecutive pump the pedal became stiffer and stiffer until there was no travel. I held my foot on it for 15 seconds or so and the pedal did not sink at all. So that should rule out the problem with the MC seals.

I also tested the brake booster with the three methods I mentioned above. It passed test 2 and 3, but not exactly test 1. For test 1, I pumped the brakes while the car was off until it became very firm. I kept my foot on the pedal with light pressure and started the car. As soon as the engine turned over, the brake pedal softened. However, it definitely sinks more than the suggested 1/4". I think it was closer to two inches, and if I continued to apply more pressure, the pedal would go further down.

While I'm exhibiting all these issues, the one thing that is working correctly is that the brake pedal will always spring back after I press down on it. I read some posts describing how when the MC or brake booster goes bad, the pedal may sink down to the floor and not come back up on its own. This is not the case with my car.

I had my brother test out the same scenarios on his Honda Accord, that has never received a brake flush, and he is exhibiting the same results as me. I am convinced that air simply got inside the system.
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Old 11-12-2018, 02:43 PM
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Is the HF device a pressure or vacuum system?
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Old 11-12-2018, 02:55 PM
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afrayedknot
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Originally Posted by Jsolo View Post
Is the HF device a pressure or vacuum system?
I believe it's a pressurized system that needs to be attached to an air compressor/air tank. This is the one I am looking at - https://www.harborfreight.com/brake-...der-92924.html
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