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Mitsubishi 4M40 engine: known problems

Used in 3 guides · 2835cc diesel · 8 known problems

Displacement

2835cc

Layout

I4 turbo

Fuel

diesel

Known problems8

Everything our guides list for the variants with this engine: the engine itself plus the gearbox and ancillaries it's paired with. Each shows which cars it's listed for.

High

Timing chain upper guide wear / chain stretch

The plastic upper timing chain guide wears thin and can break away; fragments can jam the chain and cause it to jump timing, with major engine damage. A 'trac-trac' rattle at idle is the warning sign.

Fix: Replace the upper guide (and chain/tensioner as needed) and check valve clearance around 90,000-150,000km; investigate any timing rattle promptly.

From 150k+ km · ~$800-2500

Listed for: Mitsubishi Pajero NA-NG / NH-NL

High

Head gasket failure from overheating

Like the 4D56, the 4M40's high compression makes head-gasket and cracked-head failure likely if it has been run hot - cooling neglect is the usual cause.

Fix: Machine/replace the head with a quality gasket; fully restore the cooling system (radiator, thermostat, viscous fan).

From 150k+ km / any overheat · ~$1500-3500

Listed for: Mitsubishi Pajero NA-NG / NH-NL

High

Overheating / cracked cylinder head

The 2.8 4M40 has a well-known habit of overheating and cracking the cylinder head, particularly when worked hard or with a tired cooling system.

Fix: Keep the cooling system fresh (radiator, thermostat, coolant); pressure-test and inspect the head before purchase. A cracked head means a rebuild or replacement.

Any (worse if cooling neglected) · ~$2000-5000

Listed for: Mitsubishi Pajero NM-NP

Medium

Injector and injection pump wear

Mechanical injectors and the pump wear at high km, causing hard starting, smoke and lost power.

Fix: Diesel-specialist injector and pump service; many have already been done - ask for records.

From 250k+ km · ~$1200-2800

Listed for: Mitsubishi Pajero NA-NG / NH-NL

Medium

Underpowered / strained when loaded

At 92kW the 2.8 struggles to move a heavy wagon when loaded or towing, leading owners to push it hard - which compounds the overheating risk.

Fix: Don't overload; prefer the 3.2 DiD if you need to tow or load heavily.