Rear Brakes Are Grinding

[Scorpio64 5,147]

About a week ago my rear brakes started making a grinding noise.  My first thought was that the pads wore down and now it's metal on metal.  But, there are two tiny problems with that assumption.  1) The pad wear indicators never squealed to let me know the pads were worn.  2) The pads are not worn out, I took the car to a mechanic and he said the brakes are fine and the pads still have 70% pad thickness.

 

Each day, after driving and braking a few miles, the noise seems to go away until the car sits for a while.  I was thinking oxidation can cause noise but just sitting overnight does not seem like enough time for rust to set in.

 

So, I'm at a loss.  I need a second opinion.  Besides worn pads, what else causes grinding noises in brakes?

[T Bill 649]

Sounds like rust to me.  Rotor face will rust somewhat overnight, along with the rotor edges. The pad maybe scraping the rust off the overlapping edge. If they are aftermarket pads, some do make a grinding noise when first applied in AM.   No weird smells?, keep driving.  

[Scorpio64 5,147]

Sounds like rust to me.  Rotor face will rust somewhat overnight, along with the rotor edges. The pad maybe scraping the rust off the overlapping edge. If they are aftermarket pads, some do make a grinding noise when first applied in AM.   No weird smells?, keep driving.  

 

I too suspected rust, but why all of the sudden.  I've been driving this car for over a year and the rotors just now decided to rust.  It don't add up.

[Krdshrk 3,877]

I too suspected rust, but why all of the sudden.  I've been driving this car for over a year and the rotors just now decided to rust.  It don't add up.

Pad wear with pad dust will cause rust.  Also it's been very wet/humid lately too.

 

Certain brake rotors and pads will cause this more than others.  If you have Ceramic pads, it will happen less.

[T Bill 649]

It's the end of the winter cycle. road salts, and the like.  Plus wear may be just to that point.  Who knows, mechanic says its's OK.

[DonG 0]

Its because the steel used for the actual rotors is from CHINA...   If you put the cheapest rotors on they are made out of crap and rust in a day!!!  not saying its your doing, but food for thought.  "Happens to a lot of people" Did you have the rotors replaced last time you had brake service ?

[djg0770 481]

no rotors are made of crap.  Research has been done and it's 100% certain that excrement can not be forged into rotors regardless of the amount of alloy added to the feces.

[Njbanshee 9]

I blame the new liquid crap they spray all over the roads before it snows.

[Scorpio64 5,147]

Well, I just got back from a milk run.  I inspected the rotors before I left and there was a small amount of rust speckling the rotors.  I fixed it good though, I sprayed WD40 and motor oil all over the entire brake system. 

[1563621 388]

Well Done!!!

[fishnut 2,358]

Wait, you sprayed oil all over your roters and pad? Umm you don't want oil on your roters or pad!

[T Bill 649]

  

[1LtCAP 4,262]

pull one of the tires, and then the caliper. make sure that the pads are moving freely in their slides. what may be happening, is that they're not moving freely, till they warm up a bit. they may be holding too much against the rotor, thus making noise.....other than that, i'd hafta see it.....

[Scorpio64 5,147]

pull one of the tires, and then the caliper. make sure that the pads are moving freely in their slides. what may be happening, is that they're not moving freely, till they warm up a bit. they may be holding too much against the rotor, thus making noise.....other than that, i'd hafta see it.....

 

The grinding is only when the brakes are applied.  I don't hear any noise when coasting slowly (cold or hot) so I don't believe the caliper is hanging up.  Good guess though.. 

[weekend_junkie 129]

Well, I just got back from a milk run. I inspected the rotors before I left and there was a small amount of rust speckling the rotors. I fixed it good though, I sprayed WD40 and motor oil all over the entire brake system.

Try removing the brake pads next, but only one side at a time. That will help to accelerate the wear so your mechanic can fix something.

 

My guess? The flasher fluid in your dummy lights are low.

[Scorpio64 5,147]

Try removing the brake pads next, but only one side at a time. That will help to accelerate the wear so your mechanic can fix something.

 

My guess? The flasher fluid in your dummy lights are low.

 

We'll see how the oil works out first.  If that does not fix it then I'll just take the pads off the rear brakes all together.  No pads, no grinding, Man, that grinding is annoying as hell.

[Malsua 1,422]

Every car I own or have owned, new or old gets surface rust on the rotors on humid and/or rainy days.   It growls a little for the first few stops then it's fine.

 

If you're getting metal on metal grinding, then  you've got something broken, often a stuck caliper pin or less frequently, a stuck caliper piston.

[PeteF 1,044]

Caliper pin(s) are sticking.   Inspect for torn caliper boots.  Loosen caliper nuts and try to spin them, they should turn easy.  Take apart clean the holes.  New pins, boots, and lube.   ~1 hour for both sides.

 

PS: A .38 brush works good to clean the holes.

[Schrödinger's cat 87]

Speaking of which, I put anti seize on my caliper pins because the tiny packet of grease included with the pads was only enough for one side. From what I'm reading on the internet I better get that changed before they start sticking.

[Malsua 1,422]

Speaking of which, I put anti seize on my caliper pins because the tiny packet of grease included with the pads was only enough for one side. From what I'm reading on the internet I better get that changed before they start sticking.

 

If the boots are good, chances are you're not going to have any issue.  I'll also add that you really don't want a huge amount of anti-seize on the pins.   If you're doing your own brakes, buy a bottle of the stuff make sure it's good to 1600+ degrees.   Repeated heavy braking can cause very high temps, 1200+.   You can also put a little bit on the rotor/hub mating surface and on the face of the rotor to the wheel.    The next time you change tires or rotors, they come right off, no persuasion with a hammer required.

[1LtCAP 4,262]

very few things piss me off more than taking brakes apart and finding that some backyard mechanic put anti-sieze all over everything on them. that shit doesn't belong on the pins or slides. it wastes my time when i hafta clean that shit out of there to lube them properly.

[Schrödinger's cat 87]

Yup. It was a little painful, but I did buy the small bottle of 3m silicone paste for $30. Although the pads and rotors will get very hot I'm not sure that the slide pins get as hot. Either way I'll change it soon.

[Malsua 1,422]

very few things piss me off more than taking brakes apart and finding that some backyard mechanic put anti-sieze all over everything on them. that shit doesn't belong on the pins or slides. it wastes my time when i hafta clean that shit out of there to lube them properly.

 

I have a tub of CRC brake caliper grease that I bought 15 years ago, a little goes a long way.

[Kevin125 4,772]

very few things piss me off more than taking brakes apart and finding that some backyard mechanic put anti-sieze all over everything on them. that shit doesn't belong on the pins or slides. it wastes my time when i hafta clean that shit out of there to lube them properly.

 

Only thing I use anti-seize on in the brake area is the disc locking screw that pins the rotor to the hub. Copper anti-seize in this case.  I can't recall if my Ford has that... I think it uses a retainer of some sort.  But the BMW X5 uses a allen head bolt that goes through the rotor.  Factory covers it with copper anti-sieze.. So I do the same.