Mitsubishi Delica: 4M40 EGR cooler cracking and coolant contamination

The exhaust gas recirculation cooler fitted to later 4M40 engines is prone to internal cracking caused by thermal fatigue from repeated hot/cold cycles. A cracked cooler allows coolant to enter the EGR circuit and be drawn into the intake manifold, leading to gradual coolant loss and, in severe cases, hydrostatic lock risk. This is a well-documented failure mode across the 4M40 engine family in Pajero, Triton, and Delica applications.

• Sweet-smelling white steam from the exhaust at operating temperature
• Unexplained coolant loss with no visible external puddle
• Coolant reservoir showing discolouration or oily sheen from combustion by-products

1. 1

   Check coolant reservoir level and colour for contamination.

2. 2

   Inspect the EGR cooler body and hose connections for external coolant weeping.

3. 3

   If a workshop inspection is possible: Perform a cooling system pressure test and watch for unexplained coolant loss.

4. 4

   Remove the intake pipe downstream of the EGR and look for coolant residue or a sweet smell.

Parts involved: EGR valve.

$700 to $1,800 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, 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.

• “Has the coolant level been stable, and when was the coolant last replaced?”
• “Has the EGR system been inspected or blanked?”
• “Has the vehicle ever overheated or lost coolant unexpectedly?”

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.