2006-2007 Lexus GS300 Brake Noise: Squeal, Grinding and Pulsation Causes

By Core Brake Parts Tech Team — Circleville, OH warehouse

Most brake noise on a 2006-2007 Lexus GS300 comes from three places: pads that have not bedded or have lost their noise shims (squeal), pads worn down to the backing plate or a seized rear caliper slide pin (grinding), and rotors with uneven thickness (pulsation you feel in the pedal and steering wheel). The good news is that each noise points to a specific part, so you can diagnose it at home before you buy anything. One thing is not a noise at all but matters more: a soft pedal with the brake warning lamp lit on a 2006 GS can be the master cylinder seal recall, and that goes to a dealer first.

How the GS300 Brakes Work and Why They Make Noise

The 2006-2007 GS300 uses disc brakes at all four corners: a caliper squeezes two pads against a cast iron rotor at each wheel. Wagner's brake engineers put the root cause of almost all brake noise plainly: vibration. When the pad, caliper, bracket and rotor vibrate against each other at the right frequency you hear it as a squeal; when metal touches metal you hear a grind; and when the rotor is not the same thickness all the way around, the vibration comes up through the pedal instead of the air.

That is why noise fixes are almost always mechanical: shims and insulators that damp vibration, clean and lubricated contact points, slide pins that move freely, and rotor faces that are flat and parallel. EBC notes that squeal can happen with any pad type or brand on almost any vehicle, so a noisy GS is not necessarily a bad pad, just a brake that is not set up to stay quiet.

Squeal: Causes and How to Diagnose It

A high-pitched squeal is the most common complaint. Work through these checks in order:

• New pads that have not bedded in. EBC says squeal on a fresh pad job typically shows up in the first 200 to 500 miles and usually goes away after that as the pad mates to the rotor. If it persists past 500 miles, a few firmer stops on a safe, empty road help finish the bed-in.
• Missing or dry shims. The shim on the back of each pad is there to damp vibration. If the old shims were thrown away or the new pads came without them, squeal is likely. Wagner recommends a thin coat of silicone lubricant on the back of constrained-layer shims, and no chemicals at all on bonded insulators, because that reduces their damping.
• Tired hardware. Anti-rattle clips and springs lose their tension from heat over time. Wagner's guidance is to replace all clips, springs and pins with the pads rather than reuse them.
• A lipped or uneven rotor. EBC points out that a used rotor with a lip at the edge or an uneven surface can double the time it takes new pads to quiet down. Run a fingernail across the rotor face from the center out; if it catches on a ridge at the outer edge, the rotor needs to be resurfaced within its minimum thickness or replaced.
• Glazed pads. A pad that has been overheated gets a shiny, glass-like surface that squeals and grips less. Glazing usually follows a dragging caliper or hard use without proper bedding.

If the squeal only happens at the very end of a stop and started gradually on pads that have been on the car a long time, check pad thickness right away. Many pads carry a small metal wear tab that is designed to squeal when the lining is nearly gone.

Grinding: Worn Pads and Sticking Rear Calipers

Grinding is more urgent than squeal. It usually means one of two things on this car.

Pads worn to the backing plate. Once the friction material is gone, steel rubs on iron and the rotor gets scored quickly. At that point the pads and rotors on that axle both need to be replaced; a scored rotor will chew up new pads and will not stop quietly.

Rear caliper slide pins that are rusty or binding. EBC describes this failure directly: corroded sliders and pins cause pad drag, the drag overheats the brake, and the result is squeal and fast wear. Wagner adds that guide pins that bind or corrode can keep the caliper from releasing, so it drags on the rotor. Signs of a sticking rear caliper on the GS include one rear wheel that is much hotter than the other after a drive, one pad worn far thinner than its partner, and a faint grinding or scraping that does not go away when you release the pedal.

The fix is to remove the caliper, pull the slide pins, clean the rust from the pins, bores and pad abutments on the bracket, replace torn boots, and relubricate with a high-temperature brake grease. Wagner also recommends cleaning rust and corrosion from the hub contact surface before refitting the rotor, because scale there causes the rotor to sit crooked and leads straight to the next problem, pulsation. EBC's own guidance is that calipers should be removed and serviced every 5 to 7 years or exchanged, which puts every 2006-2007 GS well past due if the calipers have never been touched.

Pulsation: Rotor Thickness Variation, Not Just Warping

A pedal that pulses or a steering wheel that shakes under braking is usually blamed on warped rotors. In most cases the real cause is rotor thickness variation: the rotor has become slightly thicker in some spots than others. Each time a thick spot passes through the caliper, braking force rises for an instant, and you feel that as a pulse.

Thickness variation builds up from a few sources:

• Runout at installation. Rust on the hub face or a loose wheel bearing lets the rotor wobble slightly. The wobble makes the pads brush one area of the rotor more than the rest, and over thousands of miles that wears the rotor unevenly. Wagner lists checking bearing adjustment, cleaning the hub face and checking hub runout as the first steps for vibration complaints.
• Uneven pad deposits. Pads that were never bedded, or that were held clamped on a very hot rotor, can leave patches of friction material that grip differently than the bare iron around them.
• Uneven wheel torque. Lug nuts tightened by impact gun to different values can distort the rotor hat. Tighten in a star pattern with a torque wrench to the value in the owner's manual or factory service manual.

Front pulsation shows up mostly in the steering wheel; rear pulsation is felt more in the seat and pedal. The fix is to resurface the rotors if they stay above minimum thickness after cutting, or to replace them, then bed the new pads properly. EBC notes that a used rotor cut on a quality lathe can actually perform better than a new rotor, provided the minimum thickness stamped on the rotor is respected.

The 2006 GS Master Cylinder Recall: Check This First

This one does not make noise, but it is the most important brake item on a 2006 GS. NHTSA recall campaign 10V499000 covers 2006 Lexus GS vehicles, along with some IS, RX, Avalon and Highlander models. The factory brake fluid contains polymers that lubricate certain brake components. If replacement fluid without those polymers was used during maintenance, the rubber seal at the rear of the master cylinder can dry out and curl. A small amount of fluid can then leak into the brake booster, which turns on the brake warning lamp, changes pedal feel and can gradually reduce braking performance.

The remedy is a newly designed seal installed free by a Lexus dealer. If your 2006 GS has a soft pedal or a lit brake warning lamp, run the VIN on the NHTSA recall lookup or call Lexus before you replace anything yourself. When you service the brake fluid on any GS, use the fluid type specified on the reservoir cap and in the owner's manual.

The Fix: Which Parts to Replace Together

For a quiet, lasting repair, replace pads and rotors as a set on each axle and fit new brake hardware kits so the clips and pins are fresh. You can shop brake pads and replacement brake rotors, and if a rear caliper is too seized to rebuild, look at replacement brake calipers. For drivers who want more bite from the rear, the EBC Yellowstuff rear brake pads for the 2006-2007 GS300 are a high-friction street and track compound listed for this car.

How Hard Is the Job?

A pad and rotor job on one axle of the GS300 is a reasonable driveway repair for someone with a floor jack, jack stands, a torque wrench and basic hand tools. Plan on extra time at the rear if the slide pins are rusted in, since cleaning pins, bores and bracket abutments properly takes longer than swapping pads. After the job, pump the pedal before moving the car, then bed the pads: Wagner's procedure is 20 slow-downs from 50 mph to 20 mph with light pedal pressure, allowing at least 30 seconds between each. Master cylinder work on a 2006 model should go through the dealer recall first.

Frequently Asked Questions

Why do my new GS300 brakes squeal?

New pads often squeal until they bed in. EBC says this usually settles within the first 200 to 500 miles. If it continues, check that the shims are installed, the hardware is new, and the rotors were resurfaced or replaced rather than reused with a lip.

Is grinding from the rear brakes dangerous?

Yes. Grinding usually means metal-to-metal contact or a caliper that is dragging. Both reduce braking and damage the rotor quickly. Inspect the rear pads and slide pins as soon as possible.

Do warped rotors cause pulsation on the GS300?

Pulsation almost always comes from rotor thickness variation, which is often called warping. It builds up from hub runout, rust behind the rotor and uneven pad deposits. Replacing or resurfacing the rotors and cleaning the hub faces fixes it.

Is my 2006 GS300 covered by a brake recall?

2006 Lexus GS vehicles are included in NHTSA campaign 10V499000 for the brake master cylinder seal. Check your VIN with NHTSA or Lexus to confirm whether the repair has been done.

Should I replace pads and rotors together?

For noise complaints, yes in most cases. New pads on a lipped or uneven rotor take much longer to quiet down and can pick up the old rotor's wear pattern.

Sources

1. NHTSA recall campaign 10V499000 - 2006 Lexus GS included; master cylinder seal condition, consequence and free remedy
2. Lexus Enthusiast: Lexus recall on 2006 GS 300 - warning lamp and pedal feel symptoms, redesigned master cylinder cup
3. Wagner Brake: Brake system noise - vibration as the source of noise, shim and hardware guidance, hub runout checks, burnish procedure
4. EBC Brakes: Brake squeal causes and cures - bed-in mileage, corroded slide pins, lipped rotors, caliper service interval