Parts for your 1991 Mitsubishi Pajero-Brake master cylinder

1991 Mitsubishi Pajero Brake Master Cylinder — What it does and how to look after it

Yes, a brake master cylinder is absolutely fitted to the 1991 Mitsubishi Pajero. Technical references including Mitsubishi Motors Workshop Manual (Group 35A: Brakes) for late first-gen and early second-gen Pajero/Montero models, the Haynes Repair Manual for Mitsubishi Pajero/Montero 1983–1999, and the Mitsubishi ASA/CAPS parts catalogue all detail a tandem (dual-circuit) master cylinder mounted to a vacuum brake booster on 1991 Pajero variants. These factory and aftermarket sources confirm the component’s presence and role on this model year.

The master cylinder is the heart of the Pajero’s hydraulic braking system. When the driver presses the pedal, the cylinder converts that force into hydraulic pressure, feeding two separate circuits for safety—so if one circuit has an issue, the other can still provide braking. Paired with the vacuum booster, it helps deliver strong, predictable pedal feel whether cruising around town or heading bush.

As part of regular servicing, the master cylinder and fluid deserve attention. Brake fluid is hygroscopic, so moisture build-up can corrode internals and soften pedal feel. Most owners will be well served changing fluid every 2 years or 40,000 km, using the spec on the reservoir cap (commonly DOT 4 in AU/NZ, never use DOT 5 silicone). Keep any spilt fluid off paint—brake fluid is nasty on clearcoat.

Signs the master cylinder may be on the way out include:

• Pedal slowly sinking under steady pressure at the lights
• Spongy or inconsistent pedal feel, even after a proper bleed
• Brake warning lamp for differential pressure faults
• Fluid traces at the rear of the master cylinder or inside the booster

Replacement tips: bench-bleed the new unit before fitting to save chasing stubborn air in the system. Use proper flare-nut spanners on the hard lines to avoid rounding. After installation, bleed all four wheels starting from the farthest caliper/wheel cylinder from the master and work closer. If equipped with ABS, follow the workshop procedure for cycling valves as required. Always check for leaks with firm pedal holds and confirm a solid pedal before driving.

Torque specs and bleed sequences can vary with engine and ABS fitment, so it’s best to follow the Mitsubishi workshop manual. If the booster has ingested brake fluid, consider inspecting or overhauling it as well.

Popular questions about 1991 Mitsubishi Pajero brake master cylinders

What brake fluid should be used?
Most 1991 Pajero setups are fine with DOT 4 brake fluid in Australia and New Zealand. Check the reservoir cap and the workshop manual for the exact spec. Don’t mix in DOT 5 silicone fluid. If upgrading from old DOT 3, a full flush is recommended for best results.

How can someone tell if the master cylinder is failing?
Classic signs are a pedal that slowly sinks at a stop, inconsistent brake bite across trips, or fluid weeping at the rear seal area. If repeated bleeding doesn’t restore a firm pedal and there are no obvious external leaks elsewhere, the master cylinder’s internal seals may be bypassing.

Is bench bleeding really necessary when replacing it?
Yes. Bench bleeding purges trapped air from the master cylinder before it goes on the vehicle, making the final system bleed quicker and more reliable. Skipping it often leads to a long, mushy pedal and multiple bleeding attempts.