Nissan Navara: YD25DDTi Cracked Cylinder Head and Coolant Loss

The YD25DDTi 2.5L common-rail diesel engine fitted to D40 Navaras suffers from thermally-induced cracking of the aluminium cylinder head, typically between valve seat inserts and coolant jacket passages. Rapid thermal cycling under load — particularly towing or sustained highway running — causes the casting to crack. Coolant enters the combustion chamber or oil gallery, leading to hydrolock risk and catastrophic bearing failure if undetected. Nissan Australia issued a voluntary service campaign and extended the warranty on affected cylinder heads to 10 years/200,000 km on some production runs.

• White or grey exhaust smoke under load or on cold start that does not clear
• Coolant level dropping with no visible external leak
• Oil filler cap showing white emulsion (coolant-oil mixing)
• Overheating gauge creeping up during towing or highway driving

1. 1

   Check coolant reservoir for brown oily contamination.

2. 2

   Inspect oil filler cap for white mayonnaise emulsion.

3. 3

   Conduct a combustion gas (CO2) sniff test on the coolant reservoir with engine warm.

4. 4

   Request any previous head replacement history from seller.

5. 5

   Look for white exhaust smoke under load.

Parts involved: Cylinder head.

$3,500 to $8,500 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 cylinder head ever been replaced or reconditioned under the Nissan extended warranty campaign?”
• “Can you show the full service history including any coolant system work?”
• “Has the vehicle ever overheated or run low on coolant?”

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.