1997-2001 Mitsubishi Montero Brake Caliper Problems and Replacement

By Core Brake Parts Tech Team — Circleville, OH warehouse

The 1997-2001 Mitsubishi Montero uses disc brakes with calipers at all four wheels, backed by four-wheel ABS. Most caliper problems on a truck this age come down to seized slide pins, a corroded piston, or a torn boot. The fix is usually a replacement caliper, installed with fresh pads and hardware, and the axle's other caliper is normally done at the same time. Before you blame a caliper, rule out the two brake-system recalls that cover these model years.

How the Montero's Caliper Brakes Work

Factory specifications for both the 1998 and the 2001 Montero list disc brakes on the front and rear axles, with four-wheel ABS and the 3.5L V6 with four-wheel drive. So a Montero from this era has four calipers, not a front-disc, rear-drum layout. That matters when you diagnose a pull or a drag: the problem can be at any corner.

When you press the pedal, the master cylinder pushes fluid through steel lines and flexible hoses to each caliper. Fluid pressure pushes the caliper piston out against the inner pad. On a sliding caliper, the caliper body then slides on its guide pins and pulls the outer pad in against the rotor from the other side. Both pads can only clamp evenly if the pins slide freely and the piston returns cleanly when you release the pedal.

Keep in mind that the Montero Sport is a separate model with its own brake parts. Always shop by the exact model, year and trim on your registration, not just "Montero".

Symptoms of a Failing Caliper

A caliper rarely fails all at once. It usually starts to hang up, and the signs build up over a few hundred miles:

• Pull to one side. The truck drifts or pulls toward one front wheel while you brake, or even while you cruise if that caliper is dragging.
• A hot wheel and a burning smell. After a drive, one wheel is far hotter than the others and smells of scorched friction material.
• Uneven pad wear. One pad is worn much more than its partner, or the inner pad is worn at a taper.
• Noise. Squeal, scraping or grinding from one corner, often because a pad has worn to its backing plate on the side that did all the work.
• Fluid on the inside of the wheel. A wet caliper, a damp tire sidewall, or a falling fluid level in the reservoir points to a leaking piston seal or bleeder.
• Brake warning lamp. A low reservoir can turn on the brake indicator lamp.

What Causes Caliper Problems on an Older Montero

Seized slide pins

This is the most common problem. ADVICS, an OE brake supplier, names three causes of sticking slide pins: the pin sticks in its bore, the pin rusts once its grease is gone, and heat and friction damage the boot and sleeve. The symptoms it lists are brake pad noise and excessive pad wear. An ASE study guide adds that damaged pin boots and contamination are the usual root cause. It also says petroleum-based lubricant should never go on these parts, because it swells rubber. Use a synthetic brake lubricant.

Corroded or sticking piston

Brake fluid absorbs moisture over time. On a truck that is twenty-plus years old, that moisture can corrode the piston or its bore until the piston no longer retracts. The pads then stay in light contact with the rotor. The result is a constant drag, heat, and a pull to that side.

Torn dust boot

Once the rubber boot around the piston splits, water and grit reach the piston surface. Corrosion follows. On a four-wheel-drive truck that sees mud, snow or salt, look at every boot at every pad change.

Collapsed flexible hose

A brake hose can deteriorate inside and act like a one-way valve, holding pressure at the caliper after you release the pedal. It feels exactly like a stuck caliper. If you open the bleeder on a dragging caliper and the wheel suddenly spins free, suspect the hose as well as the caliper.

Recalls to Check First

Two NHTSA recalls cover these Montero model years. Both can cause brake symptoms that look like a caliper fault. Run your VIN through the recall lookup on nhtsa.gov before you buy parts.

For the 1997-1998 line recall, NHTSA lists about 61,800 vehicles. Dealers were told to inspect the front lines and reposition them if they were not centered in the hole, and to replace any line that showed wear. On a 1997-1998 Montero with a front-wheel fluid leak, check the line where it passes through the inner fender before you condemn the caliper. For the 2001-2002 booster recall, the remedy is an improved accumulator. A hard pedal on the first stop after sitting is a booster symptom, not a caliper symptom.

Diagnosing a Stuck Caliper Step by Step

1. Drive and compare. After a short drive with light braking, carefully compare the wheel temperature at each corner without touching the rotor. The dragging corner stands out.
2. Spin test. Raise the truck safely on stands. Spin each wheel by hand in neutral with the parking brake released. A wheel that is much harder to turn than its partner on the same axle is dragging.
3. Pull the pads. Compare the inner and outer pad on that caliper. The ASE guide notes that slightly more wear on the inner pad is normal, but a noticeable difference means the pins or piston need attention. A tapered pad points to a sticking pin.
4. Check the pins. Remove the guide pins. They should slide out by hand and be free of rust. Look for torn boots.
5. Check the piston and boot. Look for fluid weeping around the boot and rust on the exposed piston.
6. Rule out the hose. If the caliper releases as soon as you crack the bleeder, the hose may be holding pressure.

The Fix: Which Parts to Replace

If the pins are only dry and the boots are intact, you can clean and lubricate the pins and fit new boots from a brake hardware kit. A seized piston, a leaking seal, a pitted bore, or a pin that has rusted into its bore calls for a replacement caliper. At this age, buying a complete replacement brake caliper is quicker and more reliable than rebuilding.

What to replace at the same time:

• Both calipers on the axle. Replacing calipers in pairs keeps the clamping force even side to side, so the truck does not pull after the repair.
• Pads. Pads that sat against a dragging caliper are often glazed or heat-damaged. Fit new brake pads on the whole axle.
• Rotors. A dragging caliper overheats the rotor. If the rotor is below the minimum thickness stamped on it, is scored, or shows hot spots, replace it with new brake rotors.
• Hoses. On a truck this old, the flexible brake hoses are worth replacing along with the calipers. This also eliminates a collapsed hose as the cause.
• Fluid. Flush the system with the fluid grade printed on the master cylinder reservoir cap. Moisture in old fluid is what corrodes pistons in the first place.

How Hard Is the Job?

Replacing a caliper on a Montero is a moderate job for a home mechanic with jack stands, basic hand tools, a flare-nut wrench for the hose fitting, and a way to bleed the brakes. The front calipers are the easier pair. On the rear, work around the parking brake hardware, and make sure the parking brake is released and adjusted afterward. Torque the caliper bracket bolts, guide pins and banjo bolt to the values in the factory service manual. Use new copper sealing washers on banjo fittings.

Bleeding is the step that matters most. These trucks have four-wheel ABS, so bleed patiently until the fluid runs clear with no air at every corner. If the pedal stays soft after a careful manual bleed, have a shop with a scan tool cycle the ABS unit. Bed in the new pads before you tow or drive hard.

Frequently Asked Questions

Does the 1997-2001 Montero have rear disc brakes or drums?

Factory specifications for both the 1998 and 2001 Montero list disc brakes front and rear, with four-wheel ABS. There is a caliper at each wheel.

Should I replace Montero calipers in pairs?

Yes. Replace both calipers on the same axle so the clamping force matches side to side. A single new caliper next to a tired one can leave the truck pulling.

Can a bad brake hose feel like a stuck caliper?

Yes. A hose that has collapsed inside can trap pressure at the caliper and cause the same drag, heat and pull. If the wheel frees up when you open the bleeder, suspect the hose.

My 1997-1998 Montero is leaking brake fluid at the front. Is it the caliper?

Maybe, but check the front brake lines first. NHTSA recall 98V220000 covers front lines on these years that can chafe through where they pass through the inner fender. Run your VIN for open recalls.

What grease goes on the caliper slide pins?

Use a synthetic brake lubricant made for caliper pins. Never use petroleum-based grease, which swells the rubber boots and can cause the pins to stick again.

Sources

1. AutoDetective - 1998 Mitsubishi Montero specifications - front and rear disc brakes, 4-wheel ABS, 3.5L V6, 4WD
2. AutoDetective - 2001 Mitsubishi Montero specifications - front and rear disc brakes, 4-wheel ABS
3. NHTSA recall 98V220000 - 1997-1998 Montero front brake line chafing, units affected and remedy
4. NHTSA recall 01V254001 - 2001-2002 Montero hydraulic brake booster accumulator
5. ADVICS - Troubleshooting caliper slide pin sticking - causes, symptoms and the fix for sticking slide pins
6. Free ASE Study Guides - Sticking caliper guide pins - uneven pad wear diagnosis and lubricant guidance