Nissan Stagea: RB25DET Front Crankshaft Oil Seal Weep

The front crankshaft oil seal on high-mileage RB25DET engines commonly develops an oil weep at odometer readings above 150,000 km. The nitrile elastomer seal degrades through repeated heat cycling and contact with modern oil additives, allowing engine oil to seep past the crankshaft snout onto the timing cover and into the accessory drive belt zone. Oil saturation of the drive belts causes glazing and accelerated belt cracking, and oil ingestion into the timing chain cavity accelerates plastic guide deterioration. The leak is typically slow at first but worsens progressively as the seal lip loses contact pressure. Correction requires crank pulley removal and seal replacement with an updated viton-compound seal.

• Visible oil seepage or residue around the crankshaft pulley and lower timing cover
• Oily or glazed accessory drive belts on visual inspection
• Engine oil smell when the engine is at operating temperature
• Oil drip marks or staining on the front crossmember or subframe beneath the engine

1. 1

   Use a torch to inspect the crankshaft snout, pulley hub, and lower timing cover area for oil film or dried residue.

2. 2

   Run a finger along the inner face of the accessory drive belts to check for oil contamination.

3. 3

   Inspect the front crossmember beneath the engine for oil drip staining.

Parts involved: Timing chain.

$320 to $780 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 front crankshaft oil seal been replaced?”
• “Is there any oil leakage visible from the front of the engine?”
• “When were the accessory drive belts last inspected or replaced?”

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.