2017-2020 Lincoln MKZ Rotor Replacement: Resurface or Replace

By Core Brake Parts Tech Team — Circleville, OH warehouse

On a 2017-2020 Lincoln MKZ, a rotor can be resurfaced only if it will still be above the minimum thickness stamped on it after the cut, and only if it has no cracks, hard spots, deep grooves or heavy rust. If any of those fail, replace it. In practice, most MKZ owners doing a pad job on a car with real miles find that new rotors are the cleaner, longer-lasting choice, and rotors should always be done in pairs on the same axle.

This guide walks through how to measure an MKZ rotor, what a machine shop can and cannot fix, what is different about the rear brakes on this car, and which parts to replace at the same time.

How the MKZ Brakes Are Laid Out

The 2017-2020 MKZ uses disc brakes at all four corners. Replacement catalogs list the front rotor for these years as a 316x28 vented rotor, meaning a large vented disc with cooling vanes cast between the two braking faces. Those vanes matter: the rotor has to shed the heat of stopping a heavy, powerful luxury sedan, and a rotor that has been machined thin has less mass to absorb that heat.

The front rotors do most of the work and wear fastest. The rears are smaller and usually last longer, but they are often the ones that rust, because they do less work and the pads do not scrub the faces as hard. Many MKZs use an electric parking brake operated by a switch instead of a pedal or lever, and that changes how the rear brake job is done (more on that below).

Symptoms That Point to the Rotors

• Steering wheel shake or pedal pulsation when braking from speed. This is usually disc thickness variation, not a literally warped rotor. Tire Review notes that roughly one thousandth of an inch of thickness variation can be enough to feel in the pedal.
• A visible lip at the outer edge of the braking surface, which means the face has worn down.
• Grooves or scoring you can catch with a fingernail.
• Blue or dark heat spots, which can be hard spots in the iron.
• Heavy rust on the rear faces, often with a grinding noise on the first few stops.
• Pulling to one side under braking, which can come from rotors of very different thickness side to side, or from a sticking caliper.

One MKZ-specific check before you blame the rotors: 2013-2018 Fusion and MKZ sedans were recalled because the front brake jounce hoses could rupture and leak fluid. Kelley Blue Book reports the dealer remedy is a newer braided hose design, free of charge, and that hybrid models are not affected. If a 2017 or 2018 MKZ has a soft pedal or a wet front hose, have the VIN checked for open recalls first.

How to Measure: The Resurface-or-Replace Test

Every rotor has a minimum (discard) thickness cast or stamped into it, usually on the hat or the edge. That number, not a rule of thumb, is the limit. Check the stamping on your actual rotor, or look it up in the factory service information by VIN.

1. Measure thickness with a micrometer at several points around the rotor, about an inch in from the outer edge.
2. Subtract the cut. A lathe has to remove metal from both faces to clean them up. If the result would land at or below the minimum, the rotor cannot be resurfaced. Tire Review points out that in some states it is illegal to return a rotor to service below that spec.
3. Check lateral runout with a dial indicator, with the rotor clamped to the hub using the lug nuts. Tire Review cites a target of under 0.002 inch for even wear.
4. Look for disqualifiers: cracks, hard spots, severe grooving or heavy rust mean replacement no matter how thick the rotor is. Hard spots in particular cannot be machined out.

When Resurfacing Makes Sense on an MKZ

Resurfacing is a fair choice when the rotors are well above the minimum, the car has no pulsation complaint, and you only need a fresh surface for new pads. An on-car lathe gives the best result for a runout problem because it cuts the rotor in the same plane it spins on the hub.

The downside is that every cut removes metal you cannot get back. A thinner front rotor holds less heat, which on a heavy sedan can bring the vibration back sooner. Add the shop time to remove, machine and reinstall, and new rotors are often close in cost and start with full thickness and a factory-correct finish. Tire Review also notes that new rotors should go on as supplied: machining a new rotor only removes thickness and can make runout or the surface finish worse.

The Rear Brakes and the Electric Parking Brake

If your MKZ has a parking brake switch rather than a pedal, the rear calipers have electric actuators. Ford service information calls for putting the system into its parking brake service (maintenance) mode before rear pad work and taking it out afterward, and some Ford models need a scan tool to do it. The Auto Training Centre explains that forcing components that are meant to be positioned electronically can damage them and that post-service steps, such as letting the system set its pad clearance, are part of the job.

In short: do not try to crank or lever the rear pistons back on an electric parking brake car until the system is in service mode. Follow the exact procedure in your owner's manual or the Lincoln service information for your year. Lincoln's own guidance on the electric parking brake also refers owners to the Owner's Manual for vehicle-specific instructions.

What to Replace at the Same Time

• Pads, always. New pads on old, uneven rotors bed in poorly, and old pads on new rotors carry the old wear pattern. See our brake pads, including low-dust ceramic brake pads.
• Both rotors on the axle. Tire Review recommends pairs even if only one is worn, to keep braking even side to side. Shop replacement brake rotors.
• Hardware. Abutment clips and slide pins that are rusted or dry cause uneven pad wear and noise. A brake hardware kit is inexpensive insurance.
• Calipers if a slide or piston sticks. A rotor worn much harder on one side, or one far hotter than the other after a drive, points to the caliper. Check our brake calipers.
• Everything at once. If both axles are due, the 2017-2020 Lincoln MKZ front and rear brake kit bundles rotors and pads for the whole car.

How Hard Is the Job?

The front rotors are a moderate driveway job: remove the caliper and its bracket, pull the rotor, clean the hub face, install the new rotor, and torque everything to the values in the factory service manual. Tire Review stresses two details that prevent comebacks: wire-brush the hub and rotor hat contact faces so the rotor sits flat, and finish lug nuts with a torque wrench rather than an impact gun. Uneven lug torque is a classic cause of runout and future pulsation.

The rears are the same work plus the electric parking brake service mode, which is where most DIY trouble starts. After either axle, bed the new pads in with a series of moderate stops before any hard braking.

Frequently Asked Questions

Can I resurface the rotors on my 2017-2020 MKZ?

Yes, if they will remain above the minimum thickness stamped on the rotor after the cut and have no cracks, hard spots, deep grooves or heavy rust. Otherwise they must be replaced.

Where do I find the minimum thickness for MKZ rotors?

It is cast or stamped into the rotor itself, usually on the hat or edge. The factory service information for your VIN lists it as well.

Do I need to replace both front rotors if only one is bad?

Yes. Replacing rotors in pairs keeps braking even side to side; a large thickness difference between the two can make the car pull.

Why does my MKZ still vibrate after new pads?

The rotors likely have thickness variation or runout that new pads cannot fix. Measure them, and check that the hub faces were cleaned and the lug nuts torqued evenly.

Can I push back the rear caliper pistons by hand?

Not on an MKZ with an electric parking brake. Put the system in service mode first using the procedure for your year, or you risk damaging the actuators.

Is my MKZ part of the brake hose recall?

The front brake hose recall covers 2013-2018 Fusion and MKZ sedans, excluding hybrids. Check your VIN with a Lincoln dealer or on NHTSA's recall lookup.

Sources

1. Tire Review - Brake Rotors: When to Resurface and When to Replace - minimum thickness, runout and thickness variation figures, pairs, hard spots, new-rotor and hub-cleaning guidance
2. Dynamic Friction 2017-2020 Lincoln MKZ front rotor listing - front rotor listed as 316x28 vented
3. Kelley Blue Book - Fusion and MKZ brake hose recall - 2013-2018 front brake hose recall, remedy, hybrid exclusion
4. Lincoln - How to use the electric parking brake - EPB operation, refer to owner's manual
5. Auto Training Centre - Electronic parking brake service mode - Ford service mode before rear pad work, risks of skipping it