2017-2019 Genesis G90 Brake Caliper Problems and Replacement

By Core Brake Parts Tech Team — Circleville, OH warehouse

Most brake caliper problems on a 2017-2019 Genesis G90 come down to three things: slide pins or pad guide pins that stop moving freely, a piston that leaks or sticks, and rear calipers that were serviced without first putting the Electronic Parking Brake into its service mode. Genesis addressed all three in a dealer bulletin written for the 2017-2018 G90, and the same practices apply to the 2019. This guide walks through how the G90's calipers work, how to tell a bad caliper from a worn pad, and what a proper replacement involves.

How the G90's Front and Rear Calipers Work

A caliper turns hydraulic pressure into clamping force. When you press the pedal, brake fluid fills the caliper bore, the piston extends, and it squeezes the pad against the rotor. When you release the pedal, the piston seal pulls the piston back slightly and the pads should stop touching the rotor. Anything that interferes with that release - corrosion, dried lubricant, a swollen seal - leaves the pad dragging.

Genesis bulletin 21-BR-002HG, which covers the 2017 and 2018 G80 and G90, describes two front caliper designs across those cars:

• Floating calipers have piston(s) on the inboard side only. The whole caliper slides on two greased slide pins inside rubber boots so both pads clamp evenly.
• Fixed calipers are bolted rigidly to the knuckle with pistons on both sides of the rotor. The pads ride on guide pins held by locking retainers, and nothing slides.

You can tell which you have by looking through the wheel: a fixed caliper has piston bores on the outer face and no slide pin bolts on the back. The distinction matters because the service steps are different, and greasing the wrong part is one of the most common causes of noise and dragging.

At the rear, every G90 in these years uses an Electronic Parking Brake (EPB). An electric actuator on each rear caliper drives the piston out to hold the car, and the owner's manual notes that with Auto Hold on, the EPB applies itself when the engine is shut off. That actuator is the reason rear caliper work on a G90 is not a basic pad slap.

Symptoms of a Failing Caliper on a G90

ADVICS, an OE brake supplier, lists pad noise and excessive pad wear as the main symptoms of a sticking slide pin, and traces it to pins that rust once their grease is gone, or to boots and sleeves damaged by heat and friction.

The Leak That Is Not a Leak: Ink Smear Test

New and remanufactured calipers are assembled with an oil that can seep out around the piston boot and look exactly like a brake fluid leak. The Genesis bulletin gives a simple test before anyone condemns a caliper:

1. Without disturbing the caliper boot, collect a sample of the fluid with a cotton swab.
2. Draw several horizontal lines on paper with an ink pen.
3. Wipe the sample down across the lines.
4. If the ink does not smear, it is assembly oil - wipe it off and move on. If the ink runs, it is brake fluid, and the source of the leak needs to be found and repaired.

If the leak is at the banjo bolt where the hose meets the caliper, Genesis calls for new copper washers on that fitting rather than a new caliper.

Causes: Why G90 Calipers Stick

• Dry or corroded slide pins (floating calipers). Road salt and water get past a torn boot and the pin rusts in its bore.
• Too much grease on slide pins. The bulletin warns that over-lubricating traps air at the end of the pin, creating an "air spring" that pushes the caliper back and makes the pads drag.
• Grease on fixed-caliper guide pins. On fixed calipers, Genesis says to clean the pad guide pins without abrasives and not to grease them unless the shop manual says so. Grease there collects debris.
• Rust on the pad abutments. Corrosion under the pad retainers pinches the pads so they cannot slide back.
• Old, wet brake fluid. Brake fluid absorbs moisture over time, which corrodes the piston and bore from the inside. The bulletin warns that using non-genuine DOT 3 or DOT 4 fluid can cause corrosion and shorten system life, and that the correct fluid is the one specified in the shop manual.
• Rear calipers forced back without EPB service mode. Pushing an EPB piston back with a C-clamp can damage the actuator or the piston's internal screw.

Replacing a G90 Caliper: The Right Procedure

Front

On a floating caliper, remove, clean and inspect the slide pins and boots, then apply the silicone paste specified for slide pins - sparingly. On a fixed caliper, clean and inspect the guide pins, locking retainers and pad springs instead. In both cases, clean corrosion off the pad contact surfaces with a wire brush and apply a light coat of anti-seize brake lube there, always use the new retainers or springs supplied with new pads, never reuse old shims, and install the pad with the wear indicator on the inboard side. Never let the caliper hang by its brake hose.

Rear (EPB)

The bulletin's order is specific:

1. Put the EPB into Brake Pad Change Mode with a scan tool to release the rear calipers.
2. Disconnect the EPB actuator before removing the caliper from its bracket.
3. Retract the piston by rotating it, not by pushing it straight in.
4. Reassemble, then use Brake Pad Change Mode to apply and release the EPB three times.
5. Run the EPB Assembly Check function. Genesis calls for this after replacing rear pads, a rear caliper, an EPB actuator or the EPB control module.

If you do not have a scan tool that supports the G90's EPB functions, the rear is a job for a shop that does.

Bleeding and finishing

Any caliper replacement opens the hydraulic system, so it must be bled. Keep the reservoir above the halfway point between MIN and MAX the whole time - if it drops lower, air can enter and the bleed has to start over. Use fresh fluid of the type in the shop manual, never reuse drained fluid, and wash any spilled fluid off paint immediately. The bulletin lists bleeder screw torque at 6.9-12.7 N.m (5.1-9.4 lb-ft); every other caliper and bracket bolt goes to the value in the factory service manual. Finish with the bed-in procedure: from 50 mph, brake moderately to 10 mph about ten times in a row with minimal cooling between stops.

What to Replace at the Same Time

• Pads on both sides of the axle. A stuck caliper glazes or tapers its pads, and the owner's manual says pads should always be replaced as complete front or rear axle sets. For the front, see our 2017-2019 Genesis G90 front ceramic brake pads, or browse all brake pads.
• Rotors if they are scored, heat-spotted or under minimum thickness. Genesis says to measure at eight points around the rotor before and after machining. Shop brake rotors.
• Calipers in pairs. Replacing only one caliper on an axle can leave uneven clamping from side to side. See our brake calipers.
• Hardware. New slide pin boots, retainers and springs are cheap insurance. Browse brake hardware kits.
• Brake hoses if they are cracked or bulge under pressure - a collapsing hose can hold pressure on a caliper just like a stuck piston. See brake hoses.

How Hard Is the Job?

A front caliper on a G90 is a moderate DIY job for someone who has done brakes before and can bleed a system properly. The rear is harder, not because of the hardware but because of the EPB: without a scan tool that can run Brake Pad Change Mode and the Assembly Check, you risk damaging the actuator or leaving the car with a parking brake fault. Many owners do the fronts themselves and have the rears done by a shop with the right tool.

Frequently Asked Questions

Can I push the rear caliper piston back with a C-clamp on a G90?

No. The rear calipers have an Electronic Parking Brake. Genesis calls for releasing them with Brake Pad Change Mode, disconnecting the actuator, and retracting the piston by rotating it.

Is fluid around my caliper boot always a bad caliper?

Not always. New calipers carry assembly oil that can seep out. Genesis uses an ink smear test: if the fluid does not smear ink, it is assembly oil, not brake fluid.

Should I grease the pins on the front calipers?

It depends on the caliper. Floating calipers get a light coat of silicone paste on the slide pins. Fixed calipers should have their pad guide pins cleaned, not greased, unless the shop manual says otherwise.

Do I have to replace both calipers?

It is recommended to replace calipers in axle pairs and pads always as a full axle set, so braking stays even side to side.

What does the high-pitched squeal from my G90's brakes mean?

Per the owner's manual, a high-pitched sound from the front or rear brakes signals worn pads. It is not usually a caliper fault, but check for a sticking caliper if one pad wore much faster than the others.

Why does my rear brake engage when I turn the car off?

With Auto Hold on, the G90's Electronic Parking Brake applies automatically at engine shutoff. That is normal operation, not a stuck caliper.

Sources

1. Genesis TSB 21-BR-002HG, Brake Service Best Practice Recommendations (NHTSA) - floating vs fixed front calipers, EPB Brake Pad Change Mode and Assembly Check, slide pin lubrication, ink smear test, bleeding and bleeder torque, bed-in procedure
2. 2017 Genesis G90 Owner's Manual, brakes section (ManualsLib) - pad wear indicator sound, axle-set pad replacement, EPB and Auto Hold operation
3. ADVICS - Troubleshooting: Caliper Slide Pin Sticking - symptoms and causes of sticking slide pins
4. Cardone - Brake Caliper Function and Common Failures - how caliper hydraulic pressure clamps the pads