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  #1  
Old 10-08-2011, 10:15 PM
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Default Brakes making scratching noise when backing down hill

Hi everyone. My rear brakes seem to be making a scratching noise when I am backing down a steep hill with it in neutral to my parking space (car stops easier when the brakes are only fighting the vehicle's weight and gravity and not the reverse gear). It is faint and it happens when the brakes are applied going backwards only. I just had the brakes inspected several times and it passed a NY inspection. I had them checked because they were making a similar, but yet much much louder intermittent scratching noise (like a card in bicycle spokes) in the mountains when the brakes heat up from me riding them and at first the noise would be when the brakes are released, but then as they get superheated, they would continue making noise when the brakes are applied. These brakes, calipers and rotors were just replaced a year ago along with some of the lines, the master cylinder and all hoses. Each time, mechanics would tell me that there is nothing wrong with the brakes. Except one who said my rear pads were at different wear (50% on left, 25-30% on right) and I checked the rotor temps with an IR thermometer. The front left and rear right rotors were the hottest (140-180F). The front right was #3 in temperature (about 20-30F lower than the left right) and the left rear was the lowest temp (100F-140F). This is after a stop from 65mph and they were not nearly as hot as after driving in the mountains and stopping (2 or 3 out of 4 brakes were off the scale of the IR thermometer (230F).
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  #2  
Old 11-17-2011, 12:22 PM
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Here we go again. It is getting worse and in addition to the scratching noise that they make when they get hot after repeated stops as I mentioned, when I back down the driveway without using the brake, they are making the same scratching noise. There is none when driving forward unless they were hot from mountain driving or repeated stop and go driving when I am moving higher speeds and stopping several times like at repeated close traffic lights. I looked at the brakes through the wheels and they have alot of pad left and a few weeks ago when I had all the wheels off to put snow tires on, they all had good pads. I am confused. What could be the problem?

EDIT: I don't know if this is relevant, but my brakes don't seem to work well for the first few stops. After the first couple stops, the pedal seems to firm a bit and the car's stopping distance decreases. Maybe air in the system?
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Last edited by ComputerNerdBD; 11-17-2011 at 12:27 PM.
  #3  
Old 11-17-2011, 12:28 PM
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Well as far as the scratching goes i'm not sure how to answer. BUT as far as the heat goes when running downgrades try shifting to a lower gear (yes you can do it in an automatic without causing damage just don't jump to TOO low a gear for your speed) and let the engine pick up some of the weight. Also try using a process called snub braking. They teach us CDL drivers how to do it. Do a google search and i'm sure you will find the procedure. The idea is so you DONT ride the brakes and heat them up. It allows them time to cool between applications.
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Old 11-17-2011, 12:30 PM
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Pad clips rubbin' the rotor OD perhaps? I had this happen on my old '00 Bravada after a pad, rotor, caliper bracket change. The clips had somehow become more flat than they originally should have been and they scraped on the OD of the rotor. In my case, it was only in reverse on one side and only moving forward on the other. That's a fun thing to try to diagnose!

I'm beginning to think either your truck hates you or your have OCD. Maybe both. LOL
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Old 11-17-2011, 12:55 PM
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You didnt mention what your pad composition is.

If you dont have rough rotors and little dust they should be ceramic. And the rotors would be shiny and relatively smooth.
Are the pad ends beveled? If not that could be the problem.

It Could be the pad/caliper are cocking a little going in reverse. I had a rear caliper **** once which ate up everything. Except there was nothing I could find wrong with the caliper and it never did it again. I didnt even change the hardware.

Air in system results in fade big time, so I doubt you have that.
I'm having brake problems on my bird, I suspect because the P.O. used cheap semi-metallic pads and rotors from autozone. But they 'creak', not scratch or squeal at low speeds.
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Old 11-17-2011, 01:01 PM
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Mike98Blazer: I sometimes downshift if I am going slow and the brakes can't slow this thing on a steep hill. But not often.

Swartlkk: What is the rotor OD? Pad clips hitting the rotor? Is this something that can cause those clips to fail and cause a brake failure? I have had this checked 4 times since it started making noise on hills in February. How easy is this to check out myself? I think it is the rear brakes only. When it starts to get hot, it only happens when the brakes are NOT applied, but as they get boiling hot, it does it no matter what. The brakes still seem to work fine, but the noise is a bit disturbing and loud. Between May and September 2010, I had the pads, rotors, calipers, most of the lines, all hoses, the master cylinder and the fluid (several times) replaced. A caliper failed on the Garden State Parkway May 2010 twice in one weekend and the M/C was replaced after the first one. Both times it took out the whole brake system and the pedal went to the floor. The truck does hate me no matter what preventative maintenance I do to it. I even have the brake fluid changed at regular intervals. This truck is going to be in the shop for the day next week for a water pump (it started to leak more) and I am going to have them check these brakes again and possibly bleed them again since I think there could be air in the lines again. Thanks for the tip.
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Old 11-17-2011, 01:06 PM
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OD == outside diameter. Nothing bad will happen if they are what is causing the noise. It's just a sheet metal clip that is a replaceable wear surface for the pads to slide on. There are parts of the clip that extend between the caliper bracket and the rotor on either side of the rotor that can be bent weird and cause a scrapping noise. I just bent mine out a bit with a screw driver and the noise went away.
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Old 11-17-2011, 01:24 PM
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Quote:
Originally Posted by swartlkk View Post
OD == outside diameter. Nothing bad will happen if they are what is causing the noise. It's just a sheet metal clip that is a replaceable wear surface for the pads to slide on. There are parts of the clip that extend between the caliper bracket and the rotor on either side of the rotor that can be bent weird and cause a scrapping noise. I just bent mine out a bit with a screw driver and the noise went away.
Ok great. I will have the shop inspect them and bend them if they are out of alignment. I am going to make the appointment for the water pump and this. You may have just solved months of headaches for me. Thanks for the tip.

P.S. This truck may hate me, but I noticed that the problems stay at a minimum if I stay on top of them and deal with them at the first sign of trouble. That way the truck stays on the road instead of the side of it. I haven't had to call AAA for a tow before or since the brake failures in NJ that weekend (bad caliper, misdiagnosed as bad M/C) and I want to keep it that way.
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Old 11-20-2011, 01:15 AM
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This may be a bit off topic, but before I make the appointment: water pumps are mostly about the same quality, right? This guy who does most of the repairs has a good track record, but what are the chances of a bad new/reman water pump? He is charging $150 for parts and labor for the water pump and his hourly rate is about $55. Another shop charging $75 an hour said $250. I asked about the severe duty pump and he said that the part is twice as much as the standard one. My guess was that price is too good to be true, but this guy knows his stuff so I have no concerns about the workmanship whatsoever, but what about the part?

Also, I am having them check and bleed the brakes while it is there, but the last time they were bled, the rear caliper bleeders were stuck and the other shop didn't want to touch them. This was many months ago after the hoses were replaced and there was an air bubble somewhere. These calipers are 18 months old and they look alright. Would it be beneficial to soak all of the bleeders in PB Blaster before I set out to the shop (an hour away)?
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Mods: Eurotails, Cold Air Intake, B&M transmission cooler, Throttle Body Spacer, Posi-Lok, interior LEDs

Last edited by ComputerNerdBD; 11-20-2011 at 01:18 AM.
Old 11-20-2011, 01:15 AM
 
 
 
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