2002-2006 Infiniti Q45 Brake Noise: Squeal, Grinding and Pulsation Causes

By Core Brake Parts Tech Team — Circleville, OH warehouse

Most brake noise on a 2002-2006 Infiniti Q45 comes down to three things: a high-pitched squeal from pad vibration or a worn wear indicator, grinding from pads worn to the backing plate or debris trapped at the rotor, and a pulsing pedal or steering wheel from rotor thickness variation or runout. Each one has a distinct sound and feel, and each points to a different fix. This guide walks through how to tell them apart on this car and what to replace.

How the Q45 brake system is laid out

The third-generation Q45 (2002-2006) is a rear-wheel-drive sedan powered by the 4.5-liter VK45DE V8, and it uses disc brakes at all four corners. Infiniti catalogs separate left and right caliper assemblies for both the front and the rear axle on these years, so there are no rear drums to adjust and no drum-related noises to chase. That matters for diagnosis: any scraping or squealing from the back of the car is coming from a rear caliper, pad or rotor, or from the parking brake assembly, not from brake shoes rubbing a drum.

This is a heavy luxury sedan, and the front brakes do most of the work stopping it. That weight is why front rotors on the Q45 tend to show heat-related problems such as uneven pad deposits and pulsation sooner than rotors on a lighter car driven the same way.

Squeal: what it means and how to diagnose it

A squeal is vibration you can hear. Wagner describes vibration as the main source of brake noise and lists rust, distorted or loose components, and worn parts as the usual triggers. Bendix explains the mechanism in more detail: the pad and rotor couple together and vibrate at a combined frequency, and hot spots on the rotor create friction variation that feeds that vibration.

On a Q45, work through the squeal this way:

• Squeal while driving that goes away when you press the pedal - often the pad wear indicator tab touching the rotor. Pull the wheel and measure remaining pad material. If the tab is contacting, the pads are due now.
• Squeal only during light braking - typically pad vibration. Look for missing, bent or unbonded shims on the back of the pads, dry contact points where the pad ears sit in the caliper bracket, and worn anti-rattle clips.
• Squeal right after a pad job - usually pads that were not bedded in, reused hardware, or rotors that were not cleaned or resurfaced. Brembo notes that noise after replacement is quite often not a defect in the new part but a symptom of worn surrounding components.
• Squeal in the morning that disappears after a few stops - surface rust on the rotor faces from moisture overnight. This is normal and clears itself.

Grinding: the noise you should not ignore

Grinding is metal on metal or something hard trapped where it should not be. On a Q45 the common causes are:

• Pads worn through the friction material so the steel backing plate is cutting into the rotor. The rotor is usually scored past saving at that point, and both pads and rotors on that axle need replacing.
• A stone or piece of rust trapped between the rotor and the splash shield, which makes a scraping noise that may come and go with wheel rotation. A bent splash shield touching the rotor edge sounds similar.
• A seized caliper slide pin or piston holding one pad against the rotor. Wagner calls out binding or corroded guide pins as a noise source. You may also notice the car pulling to one side, one wheel much hotter than the other after a drive, or one pad worn far more than its partner.

If you hear grinding, inspect the brakes before driving much further. A pad worn to the backing plate stops poorly and can damage the caliper piston.

Pulsation: pedal or steering wheel shake when braking

Pulsation is felt more than heard. A shake through the steering wheel usually points to the front rotors; a pulse felt mainly in the pedal or seat can be the rear. Despite the common phrase "warped rotors," the usual cause is thickness variation: the rotor surface picks up uneven pad deposits or wears unevenly because it runs with too much lateral runout.

Brembo gives useful targets here. With the disc mounted, runout should not exceed 0.10 mm, and the wheel hub itself should not exceed 0.050 mm. Brembo also points to rust and dirt on the disc-to-hub mating surfaces as a cause: a little corrosion between the hub and the rotor hat tilts the rotor slightly, and that small tilt grows into thickness variation over the following miles. Wagner lists excessive rotor runout, rust on hub contact surfaces, and loose or badly adjusted wheel bearings among its noise and vibration causes as well.

That is why simply bolting on new rotors does not always cure a Q45 pulsation. If the hub face is rusty or the lug nuts are tightened unevenly, new rotors can start pulsing again within a few thousand miles. Clean the hub face to bare metal, check runout with a dial indicator, and tighten lug nuts in a star pattern to the factory specification with a torque wrench, never an impact gun.

Quick diagnosis table

The fix, and what to replace at the same time

For squeal or pulsation on a high-mileage Q45, the lasting fix is usually new pads and rotors on the affected axle, done completely. Brembo recommends replacing pads and discs together, cleaning the hub mating surfaces, installing the anti-noise shims, greasing the caliper bracket contact points, and replacing worn caliper springs. Wagner likewise recommends replacing deteriorated anti-rattle clips, springs and pins, and keeping the pads parallel to the rotor face.

• Rotors: we carry front drilled and slotted rotors for the 2002-2006 Q45 V8, and you can browse the full range of replacement brake rotors.
• Pads: a quality ceramic brake pad set is a good match for a luxury sedan that owners expect to run quiet and clean.
• Hardware: fresh clips and pins from a brake hardware kit are cheap insurance against rattles and squeal.
• Calipers: if a slide pin or piston is seized, replace the caliper with a unit from our brake caliper collection rather than just the pads.

Lubrication matters as much as the parts. Follow the pad maker's instructions: Wagner says pads with attached shims should get only a silicone-based lubricant, because a tacky compound can make the shim detach, and that chemicals applied to certain sound insulators can reduce their effectiveness.

Bedding in, and how hard the job is

New pads and rotors must be bedded in so the pad lays an even transfer layer on the rotor. Wagner's burnishing procedure is 20 gradual slowdowns from 50 mph to 20 mph with light pedal pressure, about 30 seconds apart. Brembo notes that full bedding continues over roughly the first 300 km of driving, so avoid hard stops during that stretch.

Replacing pads and rotors on a Q45 is a moderate DIY job for someone with a jack, stands, a torque wrench and basic hand tools. Take a photo of the hardware before disassembly, compress the piston slowly, and never let the caliper hang by its hose. Caliper replacement adds a brake bleed, which is best done with a helper or a pressure bleeder.

One related item worth checking while you are at it: NHTSA lists recall campaign 04V497000 for certain 2004 Q45 vehicles, in which the brake lamp switch may malfunction so the brake lights do not illuminate. Run your VIN on the NHTSA or Infiniti recall lookup to confirm the work was done.

Frequently Asked Questions

Why do my Q45 brakes squeal after I just replaced the pads?

The most common reasons are pads that were not bedded in, old clips and pins reused, missing or damaged shims, and rust left on the hub face. New pads on old, glazed rotors also tend to squeal. Bed the pads in properly and inspect the hardware before blaming the pads.

Are my Q45 rotors warped if the steering wheel shakes when I brake?

Usually the rotors have uneven thickness rather than being truly bent. The cause is often runout from rust between the hub and rotor or uneven lug torque. Replace or resurface the rotors, clean the hub, and check runout.

Does the 2002-2006 Q45 have rear disc brakes or drums?

It has disc brakes with calipers at both the front and rear axles, so rear brake noise comes from the rear pads, rotors, calipers or parking brake parts.

Is it safe to drive with grinding brakes?

No. Grinding usually means the pad friction material is gone and steel is contacting the rotor, which reduces stopping power and damages the rotor quickly. Inspect the brakes right away.

Should I replace pads and rotors together on a Q45?

On a car with noise or pulsation complaints, yes. Brake makers recommend it because new pads on worn rotors often bring back the noise or vibration you were trying to fix.

Sources

1. Wagner Brake - Brake System Noise - vibration as the main noise source, guide pins, runout, hub rust, lubricant guidance, 20-stop 50-to-20 mph burnish
2. Bendix - Brake Noise In-Depth: Causes and Prevention - pad and rotor coupled vibration, hot spots, role of shims and lubrication
3. Brembo - Noises and Vibrations - 0.10 mm disc and 0.050 mm hub runout limits, hub cleaning, replace pads and discs together, 300 km bedding
4. NHTSA Recalls - 2004 Infiniti Q45 - recall 04V497000, brake lamp switch
5. Infiniti OEM Parts - Q45 Brake Caliper - separate front and rear caliper assemblies on the 2002-2006 Q45 with the VK45DE 4.5L V8