2017-2020 Lincoln MKZ Brake Noise: Squeal, Grinding and Pulsation Causes

By Core Brake Parts Tech Team — Circleville, OH warehouse

Most brake noise on a 2017-2020 Lincoln MKZ comes down to three things: a continuous squeal or grind that means the pads are worn out, a light squeak from dry hardware or glazed pads, and a pedal or steering-wheel pulsation caused by uneven rotor thickness rather than a truly warped rotor. Lincoln's own owner manual says occasional brake noise is normal, but a continuous squeal, a metal-to-metal grind or a shudder while braking should be checked right away.

How the MKZ Brake System Works

The 2017-2020 MKZ uses four-wheel disc brakes with ABS, Brake Assist and an Electric Parking Brake (EPB). There is no parking brake lever or pedal: the parking brake is applied by a switch, and an electric actuator at each rear caliper clamps the rear pads against the rotors. The owner manual notes that the EPB makes noises during operation and that this is normal, so a short whir or buzz when you set or release the parking brake is not a fault.

The car also offers Auto Hold, which holds brake pressure at a stop and can hand over to the parking brake. When that happens the red brake lamp comes on, which the manual describes as normal. The hydraulic system is specified for DOT 4 Low Viscosity (LV) High Performance brake fluid meeting Ford specification WSS-M6C65-A2, and the maintenance schedule calls for a brake fluid change every 3 years.

Knowing which sounds are designed in helps you separate normal operation from a real problem:

Squeal: What It Means on an MKZ

Squeal is a vibration problem. Wagner's technical guidance on brake noise puts it plainly: vibration is the main source of noise in a brake system. The pad, caliper and rotor vibrate together at a frequency you can hear, and anything that lets parts move or resonate freely makes it worse.

Common squeal causes on the MKZ:

• Worn pads. A continuous squeal is one of the signs the owner manual lists for worn-out linings. Pull a wheel and check the remaining friction on both the inner and outer pad; the inner pad can wear faster and is harder to see through the wheel.
• Dry or worn hardware. Anti-rattle clips, springs and slide pins lose tension and grease over time. Corroded or binding guide pins can also keep the caliper from releasing fully, which drags the pads and adds heat and noise.
• Missing or damaged shims. The shim on the back of each pad damps vibration between the pad and the caliper. If a shim is missing, delaminated or was left off during a previous job, squeal usually follows.
• Glazed pads or rotors. Heavy braking, riding the brakes or skipping the break-in step can glaze the friction surface, which produces a sharper squeal and less bite.
• Surface rust. A car that sits outside overnight or after a wash will often squeak for the first few stops until the pads wipe the rotor clean. The manual recommends gently pressing the brake pedal a few times after driving through a car wash or standing water to dry the brakes.

Grinding: The Noise You Should Not Ignore

A grinding or metal-to-metal sound when braking usually means the friction material is gone and the steel backing plate is contacting the rotor. At that point the rotor is being damaged with every stop, and braking performance suffers. Other grinding causes include a stone or debris trapped between the rotor and the splash shield, or a pad that has worn unevenly because a slide pin seized.

If you hear grinding, inspect all four corners before driving much further. On a car that has reached this stage, plan on replacing both the pads and the rotors on that axle; a rotor that has been scored by a backing plate is rarely worth resurfacing.

Grinding or drag from the rear can also point to the Electric Parking Brake not fully releasing. If the red parking brake lamp stays on or flashes after you release it, the manual says the system has malfunctioned and should be checked as soon as possible. Do not keep driving with the parking brake dragging: Lincoln warns that driving extended distances with it applied can damage the brake system.

Pulsation and Steering Shake: It Is Rarely a Warped Rotor

A pulsing pedal or a steering wheel that shakes during braking is almost always blamed on "warped rotors," but the industry explanation is different. Power Stop's technical page explains that the main cause is disc thickness variation (DTV): when rotor thickness varies around its circumference, the pads oscillate back and forth, and that motion is felt as a pulse in the pedal. Brake and Front End notes that rotors are cast at temperatures several times higher than even aggressive braking produces, and that thickness variations as small as 15 microns (0.00059 in) can be enough to generate a driver complaint.

DTV usually starts with lateral runout, a slight side-to-side wobble of the rotor as it spins. Runout makes the pads touch one area of the rotor more than another, which leaves uneven pad deposits and uneven wear, and over thousands of miles that becomes measurable thickness variation. Sources of runout include:

• Rust or scale between the rotor hat and the hub face, so the rotor never sits flat
• Uneven lug nut torque
• A worn wheel bearing or hub mounting face runout
• A poorly resurfaced rotor

Power Stop also points out that worn suspension components can produce vibration that feels like a brake problem, so a shake that is present even when you are not braking needs a suspension and tire check, not just new rotors.

The Fix and Which Parts to Use

For a worn-pad squeal or grinding, the correct repair is new pads and new rotors on the axle, installed with fresh hardware. For pulsation, measure rotor thickness variation and runout; if the rotors are thin or have measurable DTV, replace them rather than resurfacing, and clean the hub faces to bare metal before installing the new ones.

Because the rear pads usually wear alongside the fronts, many owners replace everything at once. Our 2017-2020 Lincoln MKZ front and rear brake kit includes pads and rotors for all four corners. If you only need one axle, browse our ceramic brake pads for low dust and quiet operation, or our replacement brake rotors.

What to replace at the same time:

• Hardware and clips. A brake hardware kit is inexpensive insurance against squeal and uneven pad wear.
• Slide pin grease and boots. Clean, re-lubricate and re-boot the guide pins with a high-temperature brake lubricant.
• Brake fluid. If the fluid is due under the 3-year interval, have it changed with DOT 4 LV fluid meeting WSS-M6C65-A2 while the brakes are apart.
• Front brake hoses on recalled cars. Some 2017 and a very small number of 2018 MKZ models are included in NHTSA recall 23V-162 (Ford recall 23S12) for front brake jounce hoses that can rupture from fatigue and leak fluid. Warning signs are a change in pedal feel and travel and a lit brake fluid warning lamp. Check your VIN and have the free dealer repair done if it has not been completed.

How Hard Is the Job?

The front brakes are a standard pad-and-rotor job for anyone with jack stands, a torque wrench and basic hand tools. The rear is where MKZ owners get into trouble. Because the Electric Parking Brake actuator is built into the rear caliper, the system must be put into its service or maintenance mode (with a capable scan tool or the factory procedure) before the rear pistons are retracted. Forcing the piston back while the actuator is engaged can damage the actuator or caliper.

After installation, tighten the caliper bolts and lug nuts to the values in the factory service manual using a torque wrench in a star pattern, then bed the new pads. Wagner's break-in recommendation is a series of 20 slow-downs from 50 mph to 20 mph using light pedal pressure, with time between stops for the brakes to cool. Proper break-in lays an even layer of pad material on the rotor, which is your best protection against both squeal and future pulsation.

Frequently Asked Questions

Is it normal for my MKZ brakes to squeak in the morning?

Yes, a light squeak on the first few stops after the car sits overnight is usually surface rust or moisture on the rotors and should disappear after a few applications. A squeal that is continuous or returns every stop is not normal and points to worn pads, missing shims or dry hardware.

Why does my MKZ make a buzzing noise when I park?

That is the Electric Parking Brake motor applying the rear brakes. Lincoln's owner manual states the EPB makes noise during operation and that this is normal. It can also apply automatically when you shift into park.

Do I need a scan tool to replace the rear brake pads?

You need a way to put the Electric Parking Brake into service mode before retracting the rear pistons, either with a scan tool that supports the EPB or the factory maintenance-mode procedure. Skipping this step risks damaging the rear caliper actuators.

Can I just resurface my rotors to fix the pulsation?

Only if they stay above the minimum thickness stamped on the rotor after cutting, and only if the cause was pad deposits or mild DTV. If the root cause is hub rust or runout and it is not corrected, the pulsation will return. New rotors installed on a clean hub face are usually the more reliable fix.

What brake fluid does a 2017-2020 MKZ use?

Lincoln specifies DOT 4 Low Viscosity (LV) High Performance brake fluid meeting WSS-M6C65-A2, and the scheduled maintenance calls for changing it every 3 years.

Is my MKZ affected by the brake hose recall?

NHTSA recall 23V-162 covers certain 2013-2018 MKZ models with front brake hoses built into production up to July 19, 2017. The cars are not in VIN order, so check your specific VIN on nhtsa.gov or with a Lincoln dealer.

Sources

1. 2020 Lincoln MKZ Owner's Manual - normal brake noise statement, Electric Parking Brake and Auto Hold operation, DOT 4 LV fluid spec WSS-M6C65-A2, 3-year brake fluid interval
2. NHTSA Part 573 Safety Recall Report 23V-162 - 2013-2018 MKZ front brake jounce hose recall, cause, warning signs and remedy
3. Wagner Brake - Brake System Noise - vibration as the source of noise, hardware and guide pin checks, break-in procedure
4. Power Stop - Why Do I Have a Pulsing Brake Pedal? - disc thickness variation, lateral runout, pad deposits, suspension vibration
5. Brake and Front End - Warped Rotors Myth - rotors do not warp in normal use, runout causes, 15 micron DTV threshold