Parts for your 1991 Mitsubishi Pajero-Radiator

1991 Mitsubishi Pajero Radiator – What it does and how to look after it

Based on the 1991 Mitsubishi Pajero factory service manual (Cooling System section), the Haynes Mitsubishi Pajero/Montero 1983–1996 manual, and Mitsubishi parts catalogues covering the 4D56 and 6G72 engines, this model absolutely uses a liquid-cooled system with a front-mounted radiator. It’s a key bit of kit on both petrol and diesel variants, and many autos also run an in-tank transmission cooler within the radiator’s lower tank.

The radiator’s job is simple but critical: it sheds heat from the engine coolant so the Pajero holds steady operating temperature whether it’s crawling a fire trail or towing the boat. Coolant leaves the engine hot, passes through the core’s thin tubes and fins, and airflow—helped by the fan and vehicle speed—carries that heat away. A healthy radiator keeps detonation, warped heads and premature wear at bay, and helps the heater work properly in winter.

As part of regular servicing, it’s smart to treat the radiator as more than an afterthought. Every 12 months (or sooner if you’re working it hard or doing muddy off-road trips), give it a once-over: look for green/white crust at tank seams, wet spots around the end tanks, and any fins that are clogged with bugs or bent flat. Clean the outside gently with low-pressure water—no aggressive degreasers—and straighten light fin damage with a fin comb if needed.

Coolant should be refreshed roughly every 2 years or 40,000–50,000 km. Use quality ethylene glycol coolant mixed with demineralised water (commonly 50/50, or follow the label for local climate). Bleed the system with the heater on hot to chase air pockets, and match the radiator cap to the spec stamped on the cap or in the manual (many are around 0.9 bar). If the Pajero has an automatic, confirm your new radiator has integrated ATF cooler fittings, or plan a separate cooler if you’re upgrading.

When replacing the unit, choose an OEM-quality core (aluminium or copper-brass depending on spec), transfer the shroud and any fan switches if fitted, renew the mounts and drain plug, and pressure-test after filling. If temps still creep up, look next at the thermostat, viscous fan clutch, water pump, and timing of the purge procedure.

• Inspect for leaks, corrosion and fin blockage
• Flush and refill coolant on schedule with the right mix
• Check cap rating, hoses and clamps, replace if perished
• Pressure-test if overheating or losing coolant

Popular questions about 1991 Mitsubishi Pajero radiators

What coolant type and capacity should be used?
Most owners run a quality ethylene glycol green coolant with demineralised water at 40–50% concentration. Capacity varies by engine and configuration, typically in the 7–10 litre range. Check the service manual for your exact engine (4D56 turbo-diesel or 6G72 V6) and top up slowly while bleeding air with the heater on.

How can someone tell the radiator needs replacing?
Persistent overheating, brown or milky coolant, repeated top-ups, wet seams on the end tanks, bowed tanks, or fins that are flaking away are classic signs. A pressure test that won’t hold and an infrared scan showing cold spots across the core also point to a clogged or failing radiator.

Do automatic models use an in-radiator transmission cooler?
Many 1991 Pajero autos route ATF through a heat exchanger inside the radiator’s lower tank. When replacing the radiator, order the version with ATF ports, or fit an external cooler with proper mounting and line routing. Don’t drive with the lines open—cap them to avoid contamination.