Unresolved brake scraping sound.

Joined
Apr 29, 2017
Messages
78
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Orange County CA
In January of 2018 I had front brakes and rotors replaced on my 2002 Sienna. At that time I also have the caliper pins regressed with the proper silicone grease. Left side was very messed with extremely uneven wear on the pads due to dry caliper pins. About a month ago the right wheel started developing a subtle scraping sound when I apply the brakes. I meant to do it anyway but since it's been over two years I thought it time to regrease those caliper pins. I'm easy on my brakes so both sides had about >50% pad left. On the right side, since that's where the sound was coming from, they paid a little more attention to the condition of the rotor and the pads and so on and so forth and everything appeared fine. So the pins and ears and shims were regreased and everything put back together. The only thing is, the mechanic pulled out the lower pin too far and that is the one that has a little rubber grommet on the end. It hadvswollen and he couldn't get the pin back inbecause of it. He seemed to feel that was not needed and so just flicked it off and put the pin back in. For the life of me I don't know why I didn't question that at the time, because I'm pretty sure car manufacturers don't put on extra parts that you don't really need...especially in brake assemblies. Plus, I never knew anything about those grommets before, or that they can swell. If I had I would have bought new ones to replace them out of hand while the brake guy was in there. So, there's the history. Everything was put back together I got down the road and everything seemed fine for a couple of days and then the soft scraping sound started again. So two questions. 1. At this point, what could be causing that low scraping sound? 2. Anyone have a firm idea of what of what the grommet is fir on the lower pins of my front disc brakes? And what bad can happen if it's not there?
 
Joined
Mar 21, 2004
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Upstate NY
Get a new mechanic. The rubber on the pins (grommet or sleeve) is there to reduce rattling. If the rubber was swollen they probably used the wrong grease. But I have (and other too) had trouble pushing the pin (with rubber back) in as I think that the rubber and grease seal it and there is air at the bottom of the hole that cannot get out. I use a vise to slowly push the pin back in. Once in it moves as it should. If the pins get dry and the right grease was used then I would suspect there is a crack in the small rubber bellows that covers the pin. Cleanup up the bellows and look for cracks and tears. Better yet, clean out the hole so its spotless and use new pin and bellows greased with Syl-guide.
 
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Using too much grease is also a problem. Grease trapped in the bottom of the hole can prevent the pin from moving especially if it has a rubber end. It wasn't clear from the post but there is plenty of friction material left right now, right? After checking the brakes twice, consider seriously that the noise may not be from the brakes.
 
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Jun 28, 2003
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6,502
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My OE rear brake shoes on my '08 Accent sometimes sound like they down to the metal. I can never find a cause. But have found stuff embedded in the shoe material.
 

MichaelRS

Thread starter
Joined
Apr 29, 2017
Messages
78
Location
Orange County CA
Originally Posted by mk378
Using too much grease is also a problem. Grease trapped in the bottom of the hole can prevent the pin from moving especially if it has a rubber end. It wasn't clear from the post but there is plenty of friction material left right now, right? After checking the brakes twice, consider seriously that the noise may not be from the brakes.
Yes. I'm very easy on my brakes. Even though it's been just over two years there's a good 50% left on the pads.
 
Joined
Jan 29, 2012
Messages
587
Location
Canada
I had a very similar problem with my rear brakes. An occasional scraping that I could never figure out until I took everything apart and inspected. Chances are it's the caliper pins since you mentioned you had problems with it in the past. Check if there's any rust pitting on the caliper pins because that prevents the outer boot from sealing. If the pin has rubber damper boots, I find that it swells and easily seizes the entire pin if you use the wrong grease or even cleaner. I really haven't noticed any noise difference from removing the damper entirely which gets rid of another point of potential failure. I think it's a good idea to replace ALL brake hardware including the caliper boots. Even if they look good, the rubber loosens over time and won't seal against water as tight.
 
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