Mitsubishi Pajero: 4M41 3.2D Injector Copper Washer Blow-out and O-ring Failure

The injector copper crush washers and lower O-ring seals on the 4M41 3.2-litre common-rail diesel deteriorate under repeated heat cycles, allowing combustion gases and raw diesel to escape past the injector body into the rocker cover area. The failure is accelerated by any previous overtightening or re-use of copper washers during injector removal. Left unaddressed, blow-by gases pressurise the valve cover, push oil out through breathers, and can crack the injector bore in the head.

• Diesel smell from engine bay with no visible external leak
• White or grey smoke at idle that clears under acceleration
• Rough or uneven idle caused by one cylinder running lean due to gas escape
• Oil contaminated with diesel (dipstick shows overfull level or thin oily smell)
• Sooty carbon deposits visible around injector base when rocker cover removed

1. 1

   Smell the oil filler cap for diesel odour.

2. 2

   Check for oily residue around the injector clamp area and any white or black smoke at idle that clears under load.

3. 3

   If a workshop inspection is possible: With the engine warm, remove the rocker cover and look for sooty carbon tracking around each injector base.

Parts involved: Fuel injector.

$500 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.

• “Have any injectors ever been removed or replaced, and were new copper washers fitted each time?”
• “Has there been any oil contamination with diesel or unexplained oil level rise?”
• “Does the engine produce any white or diesel-smelling smoke at cold or warm idle?”

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.