2017-2019 Buick Lacrosse Brake Noise: Squeal, Grinding and Pulsation Causes

By Core Brake Parts Tech Team — Circleville, OH warehouse

Most brake noise on a 2017-2019 Buick LaCrosse falls into three groups: a squeak from the rear brakes on the first stops of a cold morning, a grinding sound that means worn-out pads or a rusted rotor, and a pulsing pedal caused by uneven rotor thickness. GM published a service bulletin for the cold rear squeak on 2017-2018 models, and the fix it calls for is new rear pads. Grinding and pulsation almost always mean pads and rotors, plus proper hardware and a clean hub.

Below is how the LaCrosse brake system is laid out, how to tell the noises apart, what causes each one, and which parts actually fix it.

How the 2017-2019 LaCrosse Brakes Are Built

The third-generation LaCrosse uses disc brakes at all four corners. The front calipers do most of the stopping work and wear pads and rotors fastest. The rear calipers are also discs, and they carry the Electric Parking Brake (EPB). There is no parking brake lever or pedal: you press a switch in the center console, and a motor at the rear calipers clamps the pads against the rotors. The owner's manual describes a red parking brake status light and a separate amber parking brake warning light, plus related Driver Information Center messages.

That rear EPB matters for noise work. Because the rear pads are applied by a motor as well as by hydraulics, the rear caliper piston cannot simply be pushed back with a clamp the way an older car's could. The actuator has to be retracted, with a scan tool service function or the procedure in the service information, before the rear pads come out. Forcing the piston can damage the actuator.

Telling the Noises Apart

A simple test helps: note whether the noise comes from the front or rear, whether it happens cold or warm, and whether you hear it with the brake pedal pressed or released. A noise that continues with your foot off the brake points toward a dragging caliper or a wheel bearing rather than the pads.

The Cold Rear Squeak: GM Bulletin 17-NA-326

GM issued technical service bulletin 17-NA-326, titled Rear Brake Squeak Type Noise, covering the 2017-2018 Buick LaCrosse along with 2018-2020 Chevrolet Equinox and GMC Terrain. The condition it describes is a squeak from the rear brakes when they are cold, typically on the first brake apply. GM notes the noise may not be duplicated once the brakes are warm, which is why it often disappears by the time a car reaches the shop.

The correction in the bulletin is to replace the rear brake pads, following the Rear Disc Brake Pads Replacement procedure in GM service information, with the latest part number looked up by VIN. The bulletin lists 0.9 hours of labor for the LaCrosse. Repairs under the bulletin may have been covered by the new-vehicle warranty, but on a car this age most owners will do the pad swap themselves or pay a shop.

If your LaCrosse has this morning-only squeak and the pads still have plenty of material, a fresh set of quality rear pads with new abutment clips is the direct fix. The 2019 model year is not listed on the bulletin, but the same diagnosis applies if the symptom matches.

Squeal and Grinding: Causes and Fixes

Wagner's technical guidance puts it plainly: vibration is the main source of brake noise, and that vibration usually comes from rust, distorted or loose parts, or worn-out components. On a LaCrosse that has seen a few winters, these are the common culprits:

• Worn anti-rattle clips and springs. Heat weakens them over time, letting the pads buzz in the bracket. Replace them at every pad job; they come in most brake hardware kits.
• Rust on the caliper bracket. Scale where the clips sit pushes the pads out of line and can make them stick. Wire-brush the abutments clean before new clips go on.
• Binding guide pins. Corroded or dry slide pins cause pad drag, uneven wear and noise. Clean them and use a high-temperature brake lubricant.
• Shims and insulators. Follow the pad maker's instructions. Some pads want a light coat of silicone brake lubricant on the back of the shim; others with built-in insulators must stay completely dry.
• Dirty new rotors. New rotors should be washed with soap and water and a bristle brush before installation to remove grit and protective oil.
• Worn-out pads. When the friction material is gone, the steel backing plate cuts into the rotor. That grinding means the rotor is damaged and both pads and brake rotors need replacement.

After installing new pads, bed them in. Wagner recommends 20 slow-downs from 50 mph to 20 mph with light pedal pressure, allowing 30 seconds between stops. Skipping this step is a common cause of squeal and uneven pad transfer on a brand-new brake job.

Pulsation: Rotor Thickness Variation

A pedal that pulses under your foot, or a steering wheel that shakes when you brake from highway speed, is usually blamed on warped rotors. The real cause is almost always disc thickness variation (DTV): the rotor becomes slightly thicker in some spots than others. Power Stop explains that as those uneven spots pass through the caliper, the pads oscillate and the pedal pulses. It lists uneven clamping, rotors installed incorrectly, improperly positioned calipers, irregular friction patterns, and rust and dirt deposits as causes, and notes that thickness variation beyond .006 inch indicates the rotor needs replacement, while smaller variation may be corrected by resurfacing.

Prevention is mostly about installation:

• Clean all rust from the hub face before the rotor goes on. Rust scale behind a rotor creates runout, and runout turns into thickness variation over the following miles.
• Torque lug nuts in a star pattern to the factory specification with a torque wrench, not an impact gun.
• Bed in new pads so they lay down an even transfer layer.
• Replace pads and rotors on both sides of the axle.

Worn suspension bushings can cause a similar vibration, so if new rotors do not cure the shake, have the front suspension checked.

The Rear Caliper Recall on 2018-2019 Models

NHTSA recall 18V576000 covers certain 2018-2019 Buick LaCrosse vehicles along with a long list of other GM models. The rear brake caliper pistons may have an insufficient coating that lets gas pockets form, potentially reducing rear brake performance. The remedy was for dealers to bleed the brake system free of charge. This recall is not a noise issue, but anyone servicing the rear brakes on a 2018-2019 LaCrosse should run the VIN through NHTSA's recall lookup and confirm it was completed.

Which Parts Fix It and How Hard the Job Is

For the front axle, a quality ceramic pad set is the right choice for a quiet, low-dust daily driver like the LaCrosse. We carry 2017-2019 Buick LaCrosse front ceramic brake pads from Bendix, and you can browse more options in ceramic brake pads and brake pads. If the rotors are scored, under minimum thickness or causing pulsation, replace them at the same time.

What to replace together:

• Pads on both sides of the axle, never one wheel
• Rotors if grinding has scored them, if they pulse, or if they are below the minimum thickness cast on the rotor
• Abutment clips and anti-rattle hardware every time
• Brake fluid if it is dark or overdue, using the type printed on the reservoir cap

Difficulty: the front brakes are a straightforward job for anyone with basic tools and a torque wrench. The rear brakes are harder because of the Electric Parking Brake. The actuator must be retracted with a scan tool service function or the service information procedure before the piston can be moved. If you do not have a way to put the EPB into service mode, the rear job is best left to a shop.

Frequently Asked Questions

Why do my LaCrosse rear brakes squeak only in the morning?

That matches GM bulletin 17-NA-326 for 2017-2018 LaCrosse models: a rear brake squeak on the first stops when the brakes are cold, which fades once they warm up. GM's fix is replacing the rear brake pads.

Can I push the rear caliper piston back with a C-clamp?

No. The LaCrosse has an Electric Parking Brake at the rear calipers. It must be retracted with a scan tool service mode or the service information procedure first, or you risk damaging the actuator.

Is grinding after rain a problem?

Light scraping for the first few stops after the car sits in the rain is usually surface rust on the rotors and clears quickly. Grinding that continues on every stop means the pads are worn to metal and need immediate replacement.

Are my rotors warped if the pedal pulses?

Usually the rotors have uneven thickness rather than a true warp. The fix is new or resurfaced rotors, a clean hub face, and lug nuts torqued to specification.

Should I replace pads and rotors together?

If the rotors are scored, pulsing or below minimum thickness, yes. Fresh rotors with new pads give the quietest result and the most even bedding.

Sources

1. GM Service Bulletin 17-NA-326 - rear brake squeak when cold on 2017-2018 LaCrosse; correction is rear pad replacement, 0.9 hr labor
2. NHTSA recall data, 2018 Buick LaCrosse - recall 18V576000 rear caliper piston coating on 2018-2019 LaCrosse; remedy is a brake bleed
3. 2017 Buick LaCrosse Owner's Manual, Electric Parking Brake - EPB switch operation and red/amber parking brake lights
4. Wagner Brake: Brake System Noise - vibration as the main source of noise; hardware, guide pins, shims, rotor cleaning, 20-stop burnish
5. Power Stop: Pulsing Brake Pedal and DTV - disc thickness variation causes pulsation; over .006 in indicates replacement; lug torque to spec