Parts for your 1987 Mitsubishi Pajero-Thermostat

1987 Mitsubishi Pajero Thermostat — What It Does and When To Replace It

A thermostat is absolutely relevant and fitted on the 1987 Mitsubishi Pajero across its common engines (4D56 2.5 turbo-diesel, 4G54 2.6 petrol, and early V6 variants). This is documented in the Mitsubishi Pajero/Montero/Shogun Factory Service Manual (1982–1991) cooling system chapter, the Mitsubishi 4D56 and 4G54 Engine Workshop Manuals, and the Haynes Mitsubishi Montero/Pajero 1983–1996 Repair Manual, all of which outline thermostat specs, locations, and replacement procedures.

On a ’87 Pajero, the thermostat is the small but crucial valve that manages engine warm-up and keeps coolant temperatures steady. It stays shut while the engine warms, then opens around its rated temp to let coolant flow through the radiator. That means quicker warm-ups, stable heater performance on chilly mornings, and reduced engine wear from running too cold or too hot.

Because these old Mitsis are often used for touring, towing, or beach work, keeping the thermostat healthy is smart preventative maintenance. A diesel Pajero typically runs a lower opening temperature than the petrols (roughly 76–82°C for many diesels, about 82–88°C for petrol engines), so choosing the correct spec matters for drivability, heater output, and fuel economy.

Signs it’s time for a new thermostat include:

• Slow warm-up or the temp gauge barely lifting (stuck open).
• Overheating under load or at idle (stuck closed or sluggish).
• Heater going cold at highway speeds or temp swings up and down.

As part of servicing a 1987 Pajero, it’s reasonable to replace the thermostat every 5–7 years or around 100,000 km, or any time the cooling system is opened up for major work. When replacing, they’ll want to:

• Match the thermostat temp rating to the engine and climate.
• Fit a new gasket or O-ring and clean the housing faces.
• Torque the housing bolts evenly to spec and use a dab of anti-seize if appropriate.
• Refill with quality coolant that meets Mitsubishi requirements (mix to the correct ratio), then bleed air from the system.
• Pressure-test the cap and check hoses while the bonnet’s up.

Done right, a fresh thermostat keeps that first-gen Pajero running at the sweet spot—better economy, better heater, and less chance of overheating when the tracks get tough.

FAQs

What thermostat temperature rating suits a 1987 Pajero?
For many 2.5 turbo-diesels, a lower rating (around 76–82°C) is common, while petrol engines often use about 82–88°C. The exact spec depends on engine code and market, so it’s best to match the workshop manual or a reputable parts listing for the vehicle’s engine.

Where is the thermostat on a 1987 Pajero?
It’s typically inside the alloy thermostat housing at the engine end of the upper radiator hose. Remove the hose, undo the housing, and the thermostat and its gasket or O-ring will be right there. Always refit with the jiggle valve (if present) positioned as specified in the manual.

How often should the thermostat be replaced?
There’s no hard rule, but replacing it every 5–7 years or around 100,000 km is common practice, especially if doing a coolant flush, radiator replacement, or water pump. If overheating or slow warm-up shows up, test or replace it sooner.