Parts for your 1988 Mitsubishi Pajero-Brake booster

1988 Mitsubishi Pajero Brake Booster

Yes, the 1988 Mitsubishi Pajero is fitted with a vacuum brake booster. Technical sources including the Mitsubishi Pajero Factory Service Manual (1983–1991, Group 35A – Brakes, “Power Brake Unit/Vacuum Booster”), the Haynes Mitsubishi Pajero/Montero & Dodge Raider manual (1983–1995), Gregory’s Mitsubishi Pajero 1983–1991 manual, and Mitsubishi’s ASA parts catalogue all document a vacuum-assisted (servo) brake booster across 1988 Pajero variants. Petrol models use manifold vacuum, while diesels use an engine-driven vacuum pump to supply the booster.

The brake booster on a 1988 Pajero takes engine vacuum and uses it to assist the brake pedal, so the driver gets strong stopping power with less leg effort. It sits between the brake pedal and the tandem master cylinder, and when it’s healthy, pedal feel is consistent and confident, whether the vehicle’s knocking around town or descending a fire trail with a bit of weight on board.

As part of regular servicing, it’s smart to give the booster and its related bits a once-over. Keep an ear out for a constant hiss at the pedal (a sign of a diaphragm or grommet leak), and make sure the one-way check valve in the vacuum hose holds vacuum. A quick driveway test helps: with the engine off, pump the pedal a few times, hold it, then start the engine—the pedal should drop slightly as vacuum assist comes in. If pedal effort is hard all the time or the idle stumbles when braking, it’s time for deeper checks.

• Inspect the vacuum hose, grommet and check valve for cracking or loose fit.
• Look for brake fluid leaks at the master cylinder—fluid inside the booster is a red flag.
• Verify pedal free play and booster pushrod length to the spec in the workshop manual after any related work.

Replacing the booster is straightforward with basic tools, but access under the dash can be fiddly. Typically, the master cylinder is unbolted from the booster and moved aside carefully (avoid stressing or opening the lines), the clevis pin at the pedal is removed, and the booster’s mounting nuts are taken off from inside the cabin. When refitting, use a fresh gasket, confirm the check valve orientation, and recheck pedal free play. If the master cylinder has been disturbed or lines opened, bleed the brakes and verify a firm pedal before heading out. Matching the booster to the vehicle’s engine type and chassis code is important, as brackets and diameters can vary by model and market.

Popular questions about the 1988 Mitsubishi Pajero brake booster

How can someone test the brake booster at home?
With the engine off, pump the brake pedal several times to deplete any stored vacuum. Hold light pressure on the pedal and start the engine—the pedal should sink slightly as vacuum assist arrives. If it doesn’t, check the vacuum hose, grommet and one-way valve, and listen for hissing around the booster. A rock-hard pedal with the engine running often points to a failed booster or no vacuum supply.

Are diesel and petrol boosters the same on a 1988 Pajero?
They’re both vacuum-assisted units, but details can differ by engine, body style and market. Petrol engines draw manifold vacuum, diesels rely on a vacuum pump. Brackets, pushrod lengths, and booster diameters may vary, so it’s best to match by VIN or chassis code to ensure the correct fit and pedal feel.

Is it safe to drive if the booster fails?
The brakes will still work, but pedal effort will be much higher, especially at low speeds or when towing. That can catch drivers out in traffic. It’s not recommended—have the vacuum supply and booster inspected and repaired before regular driving.