Squeaking noise on rear brakes

Tiny
PAPET
  • MEMBER
  • 2014 DODGE CARAVAN
  • 3.6L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 22,000 MILES
Every time I step on the brake on my van I hear this squeaking noise on the rear. I can also hear this noise after parking and apply the parking brake. What I mean is, while it is park I try to shake and I can hear this noise. What must be the problem? Do I have to change the rear brake pads? Thanks and hoping for your most appreciated reply.
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Sunday, May 22nd, 2016 AT 5:22 PM

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Tiny
CARADIODOC
  • EXPERT
I believe what you are hearing is a squeak when you release the brake pedal. If that is correct, that is due to the shoes sliding across the backing plate as they release. It is fairly common and not a cause for concern, but since it can be annoying, the fix is to pull each shoe away from the backing plate, against hold-down spring pressure, then wipe a little high-temperature brake grease on the three "lands" or raised spots those shoes ride on.

Do not use regular grease as that will migrate around and could contaminate the friction surfaces, resulting in a real squeal when braking. Brake grease is designed to stay where you put it.
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Sunday, May 22nd, 2016 AT 8:39 PM
Tiny
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I can only hear the squeaking noise when I slow down and apply on the brakes. And I cannot hear the noise when I release the the brake.
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Monday, May 23rd, 2016 AT 7:12 AM
Tiny
CARADIODOC
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There's multiple causes of that with different symptoms. If you hear a "chirp, chirp" twice per wheel revolution, the brake drum is warped, (oval-shaped), and the shoes are both sliding back and forth on the backing plate. The brake grease will stop the squeak, but machining the drum will stop it also, plus eliminate the brake pedal pulsation that usually goes with it. If the drum is still round but the center plate is bent, you may not get a pedal pulsation.

A real common cause of brake squeak is contamination during parts assembly. In particular, grease, oil, brake fluid, even fingerprint grease, can cause this. This is mostly a problem when do-it-yourselfers did the work. Mechanics are real careful to avoid contamination.

A less-known cause of squeaking is simply using real high-quality brake pads and shoes. The better stuff is more tolerant of high temperatures that cause one form of brake fade, but that comes with a trade-off. Those linings tend to squeal, especially in humid weather. To reduce this tendency to squeal, many suppliers grind in a bevel to the leading edge of the linings to eliminate the "fingernails-on-the-blackboard" effect. That's less of a problem with drum brakes, but beveling those edges may help too.

Glazed linings often squeal. That comes from getting them too hot and the binders melt resulting in a smooth, shiny surface. The best cure that I've found for that is simply to machine the drums or rotors and leave them with a rather aggressive final cut. It will take a couple of hundred miles for those resulting grooves to wear down, and until they do, they will tend to file off the melted glue and leave fresh lining material to contact the friction surface. This works best with disc brakes because whatever is filed off gets blown away. With drum brakes, the stuff that gets ground off is trapped inside the drum and may get ground right back into the linings. Most mechanics will take a real light final cut on the drums, then use sandpaper to remove the glazed surface material from the pads. That is washed away with brake parts cleaner.

On vehicles that often sit unused for a few days or longer, rust can build up on the drums and rotors. The most common symptom is real easy rear-wheel-lockup for the first stop in the morning, then the rust is ground off and the brakes work properly for the rest of the day. If that rust gets bad enough, it can get impacted in the lining material and cause a squeal. I have an '80 Volare that regularly sits for up to a year between drives, then, at the end of my granite driveway, the rear wheels lock up and skid. That has occurred since the car was new. By the second or third stop, that skidding no longer occurs.

Some cars are just prone to brake squeal due to their design. Ford had a lot of trouble in the '70s and '80s because the "nail" and hold-down spring were not centered in the shoes, from top to bottom. They were much closer to the bottom. The larger top portion of the shoes were free to chatter and vibrate, and in some cases that got amplified by the backing plates to the point where it could be heard as a squeal. There was no fix for that, but it usually only occurred at a specific point in the life of the shoes. Squeals have to do with parts that want to vibrate based on their weight and the force holding them in place. New shoes are heavier, and worn shoes are lighter due having less friction material. Somewhere in the middle might be just the right conditions to set up a vibration that causes an audible squeal.

Related to that, some import manufacturers provide disc brake pads with a slot cut through the middle of the lining material. That turns it into two pieces that each vibrate and squeal at a frequency too high for us to hear. I've seen people use a hack saw to do that to squealing pads, but I doubt any manufacturer would accept that as a legitimate fix.

Solving squeals involves changing one of the contributing factors. All brake linings want to vibrate, and there are some products designed to glue brake pads to the calipers. The thinking is they can't vibrate if they're held tightly in place. I have never believed in that stuff because when taking the old brakes apart, it's easy to see that glue was used last time, and the pads always just fall out like normal. The glue wasn't doing anything. Almost all mechanics understand that since brake parts ARE going to vibrate, the best approach is to prevent those vibrations from being transferred into something that will amplify the sound. That means using that high-temperature brake grease on pad backing plates where they contact the calipers, on the mounting pads where the calipers sit on, and on the backing plates that drum shoes sit on. The goal of the special grease is to allow the vibrating parts to do what they're going to do anyway without the noise being amplified by other parts.

Some replacement brake pad manufacturers used to supply thick paper shims to stick to the backs of the pads to isolate the pads from the calipers. In 100 percent of those cases where those shims were used, when taken apart years later, that paper was always bunched up inside the pistons or caliper fingers. The only way that could happen is by the pads vibrating and moving. That's proof of what is happening, and proof we aren't going to stop it. We can only minimize the noise that results.

Since you have such a new vehicle, you might ask the dealer if any service bulletins apply. Dodge Dakotas in the mid '90s had a problem with a drone from the rear drum brakes, but only with the 9" drums. The fix was to bolt on a weight behind the backing plate to keep it from vibrating. That was a simple fix, ... If you knew about it. There are many other places, like transmission tail shafts, half shafts, even exhaust pipes, where elusive vibrations can occur after a counterweight was removed by someone who didn't understand why it was there.

The last thing to consider is if the squeal is the result of a normal condition, and we need to minimize its effect, or if it's the result of a problem that needs to be addressed. Most brake problems don't result in a squeal, so you're usually looking for something to change so the noise won't be as easy to hear. An example of a squeal caused by a "problem" was found on early Omnis and Horizons. It was possible to bend / stretch the parking brake cable's return spring to such an extent that the parking brake lever would hang not perfectly straight up and down. If it hung away from the backing plate a little, the "knot" at the end of the cable could rub on the center plate of the brake drum and cause a high-pitched squeal. There was no safety issue, but it could be quite annoying. That fix was also real simply, ... Once you knew what the cause was.
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Tuesday, May 24th, 2016 AT 8:21 PM
Tiny
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Thanks a lot for the info.
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Wednesday, May 25th, 2016 AT 3:40 AM

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