Parts for your 1990 Mitsubishi Pajero-Heater core

1990 Mitsubishi Pajero Heater Core — What It Does and How to Look After It

Technical sources confirm the 1990 Mitsubishi Pajero is fitted with a heater core located inside the HVAC/heater box behind the dashboard. This is documented in Mitsubishi’s factory service manuals for late-‘80s to early-‘90s Pajero (L040/L049 series), the Mitsubishi ASA/EPC parts catalogue, and third‑party manuals such as Haynes and Gregory’s for Pajero/Montero/Shogun covering these years.

• Mitsubishi Pajero/Montero Factory Service Manual, 1988–1991 (HVAC section)
• Mitsubishi ASA Electronic Parts Catalogue (Heater &, A/C group, 1990 Pajero variants)
• Haynes and Gregory’s Pajero/Montero manuals covering first‑gen models

The heater core in the 1990 Pajero plays a simple but vital role: it’s a small radiator that uses engine coolant to warm the cabin and clear the windscreen on frosty mornings. Housed in the heater box behind the dash, it gets hot coolant from the engine, and a fan pushes air across its fins to deliver warm air through the vents. Many 1990 Pajeros also use a cable‑operated heater tap or blend door to regulate temperature, so smooth cable movement and sealing matter for proper heat output.

Keeping the heater core happy comes down to healthy coolant and clean flow. Old or contaminated coolant can cause corrosion or scale, which clogs the core and knocks out cabin heat. Servicing schedules for vehicles of this era typically call for coolant replacement every 2 years or around 40,000 km (or as per the coolant manufacturer’s interval). Using the correct ethylene‑glycol coolant mix and demineralised water helps minimise corrosion. Tell‑tale signs of heater core trouble include a sweet coolant odour inside, fogging on the windscreen, damp carpet (usually passenger side), unexplained coolant loss, or weak cabin heat.

Replacement is a dash‑out job on a 1990 Pajero, so it’s smarter to bundle related tasks while it’s apart. Most workshops quote several hours of labour, it’s not hard, just time‑consuming. Best practice is to replace heater hoses and clamps, renew any O‑rings and foam seals in the heater box, and inspect the heater tap and blend door felt/foam. Always drain coolant cleanly, disconnect the battery, and protect brittle 1990s plastics. After refitting, pressure‑test the cooling system to the radiator cap rating, then refill with the correct mix and bleed it with the heater on full hot to purge air. A post‑service check for leaks and a quick road test to confirm strong, even heat will save a second tear‑down.

• Service tips:
  • Change coolant on time and don’t mix types.
  • Flush the system gently if scale is suspected, avoid aggressive chemicals.
  • Check for damp carpets and address early to protect the floorpan and looms.

FAQs

Where is the heater core on a 1990 Pajero?
It lives inside the heater/evaporator box behind the dashboard, typically accessed by removing the dash assembly. On right‑hand‑drive models, most work occurs from the passenger side for access to the heater box fasteners and pipes.

What are common signs a Pajero heater core is failing?
A sweet coolant smell in the cabin, persistent window fogging, a damp passenger footwell, poor heater performance, or gradual coolant loss are the big clues. Any of these deserve a cooling system pressure test before bigger damage sets in.

Can the heater core be bypassed temporarily?
Yes. In a pinch, the inlet and outlet heater hoses in the engine bay can be joined to keep the vehicle mobile and stop an interior leak. Cabin heat will be gone, and it’s only a short‑term fix until the core and related seals are replaced properly.