Mitsubishi L300: Cooling-system corrosion and overheating (head-gasket risk)

The L300/Express builds up internal scale and rust that blocks the radiator and causes overheating, which is worse on hills or when loaded because the cab-over layout gives the engine marginal cooling. Owners describe flushing several hundred grams of rust out of the system — clear-looking coolant does not mean a clean system. Sustained overheating readily blows the head gasket on this engine, turning a cheap flush into a big job.

• Temperature climbs on hills or under load
• Coolant loss
• Heater underperforms
• Brown or rusty coolant

1. 1

   Check the coolant colour and condition and look into the radiator for blockage.

2. 2

   Watch the temperature gauge on a loaded or uphill test drive.

3. 3

   Check the oil filler cap for a mayonnaise-like emulsion that suggests head-gasket trouble.

Parts involved: Head gasket, Body corrosion.

≈A$370 to ≈A$3,220 at independent workshop rates, shown as an approximate guide in Australian dollars. That is for this job on its own, not for the car.

An estimate, converted to Australian dollars, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Does it run hot when loaded or going uphill?”
• “When was the radiator and coolant last serviced?”
• “Has it ever had head-gasket work?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.