Nissan Pathfinder: YD25DDTi Injector Body Cracking and Oil Dilution

The Bosch common-rail injectors fitted to the 2.5L YD25DDTi engine develop cracks in the injector body at the fuel return banjo fitting or along the body casting under thermal and pressure cycling. Cracked injectors allow diesel fuel to migrate through the return circuit or leak past the copper seat into the combustion chamber, with excess fuel washing down cylinder bores into the engine oil sump. The oil level rises measurably above the full mark, the oil takes on a diesel smell and loses viscosity, and bearing surfaces run on diluted oil. Prolonged operation in this state causes accelerated bearing and cylinder wear. Nissan Australia issued a service campaign for this fault. Replacement requires new or remanufactured injectors and a full oil and filter change; if bore wash has occurred, a compression and bore inspection is warranted.

• Engine oil level rising above the full mark between services
• Diesel odour from the engine oil on the dipstick
• Increased black or blue smoke from the exhaust
• Rough idle or extended cold-start crank time

1. 1

   Check the engine oil dipstick for a level noticeably above the full mark and smell the oil for a diesel or fuel odour.

2. 2

   Inspect the injector return lines and banjo fittings at the top of the engine for weeping fuel or staining.

3. 3

   Confirm via service records whether injectors have been replaced under Nissan's service campaign.

4. 4

   Ask the seller whether the oil level has ever unexpectedly risen between services.

5. 5

   Request a compression test on all four cylinders to identify any bore wash damage.

Parts involved: Fuel injector.

$1,500 to $4,000 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 oil level ever risen above the full mark between oil changes?”
• “Have the injectors been inspected or replaced under Nissan's service campaign?”
• “Has a compression test been performed to rule out bore damage?”

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.