Why Are My Brakes Squealing? Grinding, Pulsing and More

Why are my brakes squealing?

Most brake squeals come from one of three things, and only one of them is a real warning. The trick is noticing when it happens.

If it squeals for the first few stops of the morning and then goes quiet, that's almost always surface rust. Leave a car outside overnight in a Shediac fog or after a wet snowfall and the rotors grow a thin orange film. The pads scrape it off in a few stops, and they complain while they do it. Mazda's own service advice rates this as low concern. If it's gone by the end of your street, forget about it.

If it squeals every time you brake, all day, that's different. Most pads have a small steel tab built in that touches the rotor once the friction material gets thin. It's designed to annoy you. The giveaway is a high, steady squeal with light pedal pressure that often fades when you press harder. It's not an emergency today, but it's a weeks-not-months job. Ignore it long enough and the squeal turns into a grind, and a pads-only job becomes pads and rotors.

The third cause is glazing. Pads that get too hot form a hard, shiny surface that squeals and doesn't bite as well. On a mountain road that comes from riding the brakes downhill. Around Moncton, where most hills are over before your brakes get warm, a glazed pad more often points to a caliper that isn't fully letting go.

• Squeal for a few stops, then quiet: surface rust, normal
• Steady squeal at light pressure, every drive: wear indicator, book it soon
• Squeal plus weaker stopping: glazed pads or a dragging caliper, get it checked
• Don't spray anything on squealing brakes to quiet them. Lubricant on a pad or rotor face makes the car stop worse.

Grinding brakes: what it means and how urgent it is

Grinding usually means metal on metal. The pad material is gone and the steel backing plate is rubbing on the rotor. Every stop now cuts into the rotor, and the car takes longer to stop. This one shouldn't wait. Drive it gently, skip the errands and get it looked at in the next day or two.

Not every grind is a worn-out pad, though. A stone or a chunk of winter sand can get trapped between the rotor and the thin metal dust shield behind it. That makes a scraping or grinding noise that's often there even when you're not braking, and it may change when you turn. Spring, when the sand trucks' leftovers are still on the shoulders, is prime season for this. Sometimes it falls out on its own. If it doesn't, it's a quick wheel-off job.

The one that surprises people is seized hardware. In the salt belt, rust builds up behind the pad clips and on the slide pins until a pad can't move freely. The inner pad, the one you can't see through the wheel spokes, wears down to metal while the outer pad still looks fine. We hear "but I looked at them last month" a lot. You were looking at the wrong pad.

Brake pedal pulsing or steering wheel shaking when you brake

A pedal that pulses under your foot, or a steering wheel that shimmies when you brake from speed on Wheeler Boulevard, usually means the rotors have uneven thickness. People call it warped rotors, but brake makers point out the rotor usually isn't bent. It's worn unevenly, often because pad material has built up in patches on its face. It doesn't take much. Technical guidance from Know Your Parts puts the noticeable range at 10 to 20 microns of variation, a fraction of the thickness of a human hair.

It's annoying more than dangerous at first, but it doesn't fix itself, and worn suspension parts can make it come back fast after new rotors go on. That's worth checking at the same time.

One thing that is normal: if the pedal buzzes and chatters hard during a panic stop on ice, that's the ABS doing its job. Keep your foot down and steer.

Car pulls to one side when braking

If the car steers itself left or right only when you brake, one wheel is doing more work than the other. Here that's almost always a caliper that's sticking, and road salt is usually the reason.

Most calipers slide on a pair of pins sealed in rubber boots. Once a boot tears, salt brine gets in, the pin rusts and the caliper stops floating. Either that side doesn't clamp properly or it never fully lets go. Other signs: one wheel noticeably hotter than the rest after a drive (hold your hand near it, don't touch), a hot burning smell after you park, or the car feeling like it's dragging an anchor.

Salt damage at the caliper is a known problem in this part of the country. Transport Canada has published recalls on certain vehicles registered in heavy road-salt provinces, New Brunswick among them, because the brake hose fitting at the caliper could corrode and leak or break. That's specific to those models, but it tells you what our winters do to the hardware at the wheel.

If the car pulls all the time and not only when braking, look at tire pressure first, then alignment. That's a different problem.

Soft or spongy brake pedal, or a red brake light: stop and check

A pedal that goes further than it used to, feels mushy, or slowly sinks while you're stopped at a light is a hydraulic problem, not a pad problem. That means a fluid leak, air in the system, a failing master cylinder or badly worn-out fluid. This is the one where we'd say stop driving. Have someone come to you or get it towed.

Old fluid matters more than people think. Brake fluid absorbs moisture over time, and that water lowers its boiling point. Get the brakes hot and the fluid can form vapour bubbles, which squash where fluid wouldn't, and the pedal goes soft. In the Maritimes we also see steel brake lines rust through from the outside, which can start as a slow weep and end with a sudden loss of pressure.

If the red brake warning light comes on, check the parking brake first. Ford's owner guidance says to rule that out before anything else. If the parking brake is off, the light usually means low fluid or a fault in the system. Low fluid has two causes: the pads have worn so far that the pistons have pushed out and drawn fluid down, or there's a leak. Topping it up and carrying on hides both. If the red brake light and the amber ABS light are on together, treat it as serious and don't drive.

What a proper brake check covers

A quick look through the spokes isn't a brake check. A real one takes the wheels off and looks at all four corners, because the problems hide on the inside.

If you're in Dieppe, Moncton or Riverview, we can do the check and most pad and rotor jobs right in your driveway. If the steel lines are rotten or the job needs a hoist, we take the car to a shop and manage the repair from start to finish, so you're not starting over with someone new.

• Inner and outer pad thickness at every wheel, not just the ones you can see
• Rotor surface and thickness, including the inside face and the rust ring at the edge
• Slide pins pulled, cleaned and greased, and the rubber boots checked for tears
• Caliper pistons moving freely and pads moving freely in their brackets
• Brake hoses and steel lines underneath the car, looking for rust, weeping and swelling
• Brake fluid level and condition
• Parking brake operation, especially on rear-disc cars that sit a lot
• A short test drive to feel for pull, pulsing and noise