1997-2001 Mitsubishi Montero Brake Noise: Squeal, Grinding and Pulsation Causes

By Core Brake Parts Tech Team — Circleville, OH warehouse

On a 1997-2001 Mitsubishi Montero, a high-pitched squeal usually means vibrating pads, dry or worn caliper hardware, or a wear indicator touching the rotor. Grinding means metal-on-metal and needs attention right away, and a pulsing pedal almost always points to rotor thickness variation. On the 2001 model there is one more noise to know about: a sound from the left side of the dash when you press the pedal, which was the subject of a safety recall on the hydraulic brake booster.

How the Montero Brake System Is Built (1997-2000 vs 2001)

These model years straddle two different Monteros, and that matters when you chase a noise.

• 1997-2000 (second generation): Published specifications for the 1998 Montero list vented front discs, solid rear discs and standard anti-lock brakes, paired with a 3.5-liter V6 and on-demand four-wheel drive. There are no rear drums to adjust - every corner is a disc brake with pads, a caliper and a rotor.
• 2001 (third generation): The 2001 Montero was an all-new vehicle with a longer wheelbase, wider track and a unibody chassis. Its power assist comes from a hydraulic brake booster with a nitrogen-charged accumulator rather than a conventional vacuum booster, as described in NHTSA recall 01V254001.

One naming trap: the Montero Sport is a separate, smaller model sold over the same years. Parts for a Montero Sport, such as this vacuum power brake booster for the 1997-2001 Montero Sport, do not fit the full-size Montero. Confirm which vehicle you have from the badge and registration before ordering anything.

Squealing: The Most Common Montero Brake Noise

Wagner's brake noise guide puts it plainly: vibration is the main source of noise in a brake system, and that vibration comes from rust, distorted or loose parts, or worn and weakened original components. On a heavy SUV like the Montero, which often lives on gravel roads and in salt country, all three show up.

Work through these causes in order:

1. Wear indicator contact. Many pads carry a small steel tab that squeals against the rotor when the friction material gets thin. A squeal that happens while driving and stops when you press the pedal is the classic sign. Pull a wheel and look at what is left.
2. Worn or missing anti-rattle clips and springs. Wagner notes these clips lose their tension from brake heat. A pad that can move in its bracket will buzz and squeal. Replace the hardware every time you do pads; a brake hardware kit is inexpensive insurance.
3. Rust on the caliper bracket abutments. Scale where the pad ears sit tilts the pad so it does not sit parallel to the rotor. Wagner specifically recommends removing rust and corrosion from these surfaces so the pads stay square to the rotor.
4. Shims and lubricant. Follow the pad maker's instructions: some shims take a silicone brake lubricant, some insulators must be left dry, and pads without shims need a noise-damping compound on the backing plate.
5. No break-in. New pads that were never burnished are noisy and can glaze. Wagner's procedure is 20 slow-downs from 50 mph to 20 mph with light pedal pressure, waiting 30 seconds between each.

Grinding: Stop Driving and Inspect

A grinding or growling sound under braking on a Montero this old usually has one of three sources:

• Pads worn to the backing plate. Steel is now cutting the rotor. The rotor is almost certainly scored past saving and must be replaced along with the pads. Keep going and you risk damaging the caliper piston.
• Debris caught between the rotor and the dust shield or pad. Gravel from off-road use can wedge in and grind constantly, even off the brakes. Pull the wheel and look.
• A seized caliper or slide pin. If a pin will not slide freely, one pad drags, overheats and wears unevenly. Wagner stresses that guide pins must move freely to prevent rotor drag. A caliper seized at the piston needs replacing - see our brake calipers.

A light grinding for the first few stops on a damp morning that then disappears is usually surface rust being wiped off the rotors, which is normal.

Pulsation: Rotor Thickness Variation, Not Warping

If the pedal or steering wheel shakes when you stop, the rotors are the prime suspect. Power Stop explains that a pulsing pedal comes from disc thickness variation (DTV): the rotor wears unevenly, so the pads are pushed in and out as it turns. The causes it lists include uneven clamping force, rotors not installed correctly, poorly positioned calipers, irregular friction patterns and rust or dirt deposits.

Power Stop's measurement guidance is that rotor thickness should not vary by more than .001 inch (0.025 mm) across six measurement points, and that a variation over .006 inch (0.15 mm) calls for resurfacing or replacement. Wagner adds that hubs should be checked for excessive runout and cleaned of rust, because a rusty hub face tilts a brand-new rotor and starts the problem all over again.

The fix sequence:

1. Clean the hub mounting face down to bare metal.
2. Install new or properly resurfaced brake rotors, washed with soap and water first to remove machining residue.
3. Torque the lug nuts in a star pattern to the value in the factory service manual using a torque wrench, never an impact gun alone. Power Stop calls out correct lug torque as critical to preventing uneven clamping.
4. Bed in the new pads.

The 2001 Montero Dash Noise: Hydraulic Booster Accumulator Recall

This one is unique to the 2001 model. NHTSA recall 01V254001 states that the accumulator installed on the hydraulic brake booster may have been improperly manufactured, allowing the pressurized nitrogen gas inside to leak over time. The recall notes that loss of that gas pressure could cause an abnormal noise from the left side of the dash panel when the brakes are applied, and possibly a delayed first brake assist after the vehicle has been parked. The remedy was for dealers to install an improved accumulator.

If your 2001 Montero makes a pump or buzzing noise behind the left side of the dash when you press the pedal, or the first stop after sitting feels hard, run the VIN through NHTSA's recall lookup and contact a Mitsubishi dealer to confirm whether the campaign was completed. Do not treat this as a pad or rotor problem - it is a power-assist issue and it affects stopping distance.

What to Replace Together and How Hard the Job Is

Pads and rotors on either generation are a moderate driveway job with basic hand tools, a jack, stands and a torque wrench. For a quiet, pulsation-free result:

• Replace pads in axle sets and resurface or replace the rotors at the same time. Ceramic brake pads suit a daily-driven Montero because they tend to run quieter and cleaner than semi-metallic compounds; browse all brake pads for other options.
• Install new clips and springs, clean and lubricate the slide pins, and clean the abutments.
• Inspect the flexible brake hoses for cracks while the wheels are off.
• On a 2001, leave the hydraulic booster and accumulator to a shop or dealer unless you have the service manual and the correct procedure - that system stores high pressure.

Frequently Asked Questions

Does the 1997-2000 Montero have rear drum brakes?

No. Published specifications for the 1998 Montero list vented front discs, solid rear discs and standard anti-lock brakes, so rear noise comes from pads, calipers and rotors, not shoes.

Why do my new Montero brakes squeal?

The usual causes are reused anti-rattle hardware, rust on the caliper bracket, missing shim lubricant or damping compound, or pads that were never broken in. Fix the hardware and follow the bedding procedure.

Can I just resurface pulsing rotors?

If the rotor stays above its minimum thickness after machining, yes. If it is already thin, or the variation is severe, replace it. Either way, clean the hub face and torque the wheels properly or the pulsation will return.

What is the noise under the dash on my 2001 Montero when I brake?

It may be related to NHTSA recall 01V254001 on the hydraulic brake booster accumulator. Check your VIN for open recalls and have a dealer inspect it.

Do Montero Sport brake parts fit a Montero?

Not as a rule. The Montero Sport is a different vehicle, so match parts to the exact model and year before you order.

Sources

1. NHTSA recall data, 2001 Mitsubishi Montero - recall 01V254001, hydraulic brake booster accumulator, dash noise and delayed assist, improved accumulator remedy
2. The Auto Channel, 1998 Mitsubishi Montero specifications - vented front and solid rear discs, standard ABS, 3.5L V6, on-demand 4WD
3. The Auto Channel, 2001 Mitsubishi Montero Limited review - third generation, longer wheelbase, wider track, unibody chassis
4. Wagner Brake, Brake System Noise - vibration as noise source, hardware, abutment rust, shims, hub runout, 20-stop burnish procedure
5. Power Stop, Pulsing Brake Pedal and DTV - causes of disc thickness variation, .001 in and .006 in measurement guidance, lug torque