1998-2002 Subaru Forester Brake Noise: Squeal, Grinding and Pulsation Causes

By Core Brake Parts Tech Team — Circleville, OH warehouse

Most brake noise on a 1998-2002 Subaru Forester comes from three things: a high-pitched squeal from the pad wear indicators or tired pad hardware, a grinding noise from pads worn down to the backing plate (or rust and debris between pad and rotor), and a pulsing pedal from disc thickness variation on the front rotors. Each one has a specific cause you can check in your driveway, and most are fixed with pads, rotors and fresh hardware rather than major parts.

How the First-Generation Forester Brake System Is Laid Out

The first-generation Forester uses a hydraulic, dual-circuit system with a master cylinder and brake booster feeding sliding calipers on ventilated front discs. The rear setup is where owners get tripped up: depending on the model year, trim and market it was sold in, the rear axle carries either disc brakes or drum brakes with shoes. Published spec sheets for the same model year disagree by market (a Canadian-market 1999 Forester L is listed with 4-wheel disc brakes and 4-wheel ABS), so do not assume. Look through the rear wheel spokes: if you see a caliper and a flat rotor face, you have rear discs; if you see a closed drum, you have shoes inside.

That matters for noise diagnosis, because a rear drum makes very different sounds (scraping, a dragging hum, a clunk from loose shoes) than a rear disc, and parts lookups for this generation split by rear brake type.

Squeal: Wear Indicators, Hardware and Glazing

A sharp, repeatable squeal is usually your pads telling you they are near the end. Many pads carry a small metal tab that contacts the rotor once roughly 1/8 to 1/4 inch of friction material is left, and it produces a loud squeal whenever you brake. On a Forester this age, the front pads do most of the work, so start there.

If the pads still have plenty of lining, look at the hardware. Wagner's technical guidance identifies vibration as the main source of brake noise, and points to rust, distorted or loose components, and worn original parts. The anti-rattle clips on a sliding caliper lose their spring tension with heat cycles, and a pad that can shift in its bracket will sing. Other squeal causes worth checking:

• Glazing. Pads and rotors that were overheated take on a hard, shiny surface with less grip. Glazing often follows long downhill runs or a sticking caliper.
• Missing or dry shims. The shim on the back of the pad damps vibration. Follow the pad maker's instructions exactly: Wagner calls for silicone lubricant on the back of constrained-layer shims but no chemicals at all on the insulator area of its IMI insulator pads.
• Dry slide pins. Slide pins that are not lubricated let the caliper hang up, which causes both noise and uneven pad wear. Never put lubricant on the rotor or the friction face of the pad.
• Skipped break-in. New pads that were never bedded to the rotor are a common source of noise right after a brake job.

Grinding: When It Is Rust and When It Is Damage

A brief scrape on the first couple of stops after the car sits overnight in rain or snow is surface rust on the rotor faces. It should disappear once the pads wipe the rust off. That is normal on any car with cast-iron rotors.

Grinding that happens on every stop is different. It usually means the friction material is gone and the steel backing plate is cutting into the rotor. At that point the rotor is being damaged with every stop and braking performance is getting worse. Park it and replace the pads and rotors on that axle together. A stone trapped between the rotor and the dust shield can also make a grinding or scraping noise, so pull the wheel and look before you order parts.

On Foresters with rear drums, a grinding or scraping noise from the back often means worn shoes, a broken return spring, or rust buildup on the drum lip. Pull the drum and inspect the shoes, springs and adjuster; replace the shoes as an axle set and install a new hardware kit at the same time.

Pulsation: Disc Thickness Variation, Not "Warped" Rotors

A pulsing pedal when you brake from highway speed is almost always disc thickness variation (DTV). Wagner explains that as the thicker and thinner sections of the rotor pass through the caliper, they displace fluid and push the pistons in and out, which you feel as pulsation in the pedal. Power Stop notes that a thickness variation beyond 0.006 inch (0.15 mm) may call for replacing or resurfacing the rotors.

DTV starts with lateral runout, the side-to-side wobble of a rotor as it turns. Wagner notes that most vehicles have a runout specification of two thousandths of an inch or less. When runout is excessive, the rotor touches the pad on every revolution; semi-metallic pads wear thin spots into the rotor, while ceramic pads can transfer material and build thick spots. The usual root causes on a car this age:

• Rust scale on the hub face under the rotor hat, which tilts the new rotor out of true.
• Lug nuts tightened unevenly with an impact gun instead of a torque wrench in a star pattern.
• Worn front wheel bearings, which let the rotor wobble.
• Pads not bedded in after installation.

The fix is new rotors, and the prevention is in the installation: clean the hub face down to bare metal, torque the lug nuts to the value in the owner's manual or factory service manual, check runout with a dial indicator if you have one, and bed the pads.

The Fix and Which Parts to Buy

For squeal or grinding from the front, the correct repair on a 20-plus-year-old Forester is a complete front job: pads, rotors and a new hardware kit. Old rotors on these cars are often near minimum thickness and rusted around the hat, so resurfacing rarely makes sense. Shop brake pads and brake rotors, and add brake hardware kits so the clips and pins are fresh. Ceramic brake pads are a quiet, low-dust choice for a daily-driven Forester.

If one wheel squeals constantly and runs noticeably hotter than the other side after a drive, the caliper is dragging. Replace the slide pins and boots, and if the piston is seized, replace the caliper; see our brake calipers. For rear drum cars, brake shoes and a spring kit solve most rear scraping.

What to replace at the same time: hardware clips, slide pin boots, and brake fluid if it is dark. On a car this old, inspect the rubber brake hoses for cracks while the wheels are off.

After the job, bed the pads. Wagner's procedure is 20 gradual slow-downs from 50 mph to 20 mph with light pedal pressure, allowing about 30 seconds between them. This mates the pad to the rotor and is one of the best defenses against both squeal and future pulsation.

A Recall Worth Knowing About

NHTSA campaign 99V040000 covers certain 1999 Subaru Foresters equipped with ABS. In extremely cold weather the brake pedal could go to the floor and stopping distance could increase. The remedy was replacement of the brake master cylinder by a dealer. It is not a noise issue, but if you own a 1999 and have a low or sinking pedal in cold weather, run your VIN through the NHTSA recall lookup and contact a Subaru dealer. A sinking pedal on any Forester can also point to a worn master cylinder; see our master cylinders.

How Hard Is This Job?

A front pad and rotor job on a first-generation Forester is a moderate DIY job with basic hand tools, a torque wrench and a jack with stands. The biggest time sinks are rusted caliper bracket bolts and rotors stuck to the hub; penetrating oil and a few firm hits on the rotor hat usually free them. Rear drum work takes more patience because of the springs and adjuster. If you are unsure of any torque value, use the factory service manual rather than guessing.

Frequently Asked Questions

Why do my Forester brakes squeal only in the morning?

Overnight moisture forms a light layer of rust on the rotor faces. The first few stops scrape it off and the noise goes away. If it continues once the brakes are dry, look at pad wear, clips and shims.

Is grinding safe to drive on?

No. Grinding on every stop usually means the backing plate is contacting the rotor. Braking is compromised and the rotor is being ruined. Replace pads and rotors on that axle before driving further.

Do I have rear drums or rear discs on my 1998-2002 Forester?

It depends on model year, trim and market. Look through the rear wheel: a caliper and flat rotor face means discs; a closed drum means shoes. Order parts by what is actually on the car.

Can I just resurface my rotors to fix the pulsation?

Only if they stay above the minimum thickness cast into the rotor after machining. On rotors this age that is uncommon, and Power Stop notes that new rotors are often more cost-effective than resurfacing.

Why did my new brakes start squealing right after I replaced them?

The usual causes are reused worn clips, missing or unlubricated shims, dry slide pins, or skipped bedding. Fix the hardware, then run the break-in procedure.

Sources

1. Wagner Brake - Brake System Noise - vibration as main noise source, clip tension loss, shim lubrication rules, 20-stop burnish procedure
2. Wagner Brake - Brake Pedal Pulsation and Disc Thickness Variation - DTV mechanism, runout spec of two thousandths or less, hub rust, pad material transfer
3. Power Stop - Pulsing Brake Pedal and DTV - 0.006 inch thickness variation threshold, lug torque and break-in
4. Power Stop - Causes and Solutions for Squealing Brake Pads - wear indicator at 1/8 to 1/4 inch, moisture and rust noise, lubrication rules
5. NHTSA Recalls - 1999 Subaru Forester - campaign 99V040000, ABS cold-weather pedal, master cylinder replacement
6. Auto123 - 1999 Subaru Forester L Specifications - Canadian-market listing of 4-wheel disc brakes and 4-wheel ABS