Nissan Pathfinder: Radiator Internal Partition Failure — ATF Contamination

The R51 Pathfinder's OEM radiator contains an internal automatic transmission fluid cooler separated from the coolant jacket by a plastic partition bonded into aluminium end tanks. Thermal cycling and age cause the plastic partition to crack or debond. Coolant and ATF cross-contaminate: coolant entering the transmission circuit emulsifies ATF into a characteristic pink-brown milky fluid (colloquially 'strawberry milkshake'), which destroys transmission clutch packs, seals, and the torque converter within a short period of continued driving. This failure pattern led to class action litigation in the United States. The radiator, transmission, and in severe cases the transfer case all require replacement.

• ATF dipstick showing milky, pink-brown, or foamy fluid
• Coolant reservoir showing oily contamination or brown emulsion
• Transmission shudder, slipping, or refusal to engage gears
• Overheating with no visible external coolant loss

1. 1

   With the engine cold, pull the ATF dipstick and inspect fluid closely for any milky, frothy, or brown-tinged appearance — healthy ATF is clear red.

2. 2

   Check the coolant overflow reservoir for oily contamination or brown scum.

3. 3

   Confirm via service records or visual inspection that the original plastic-tank radiator has been replaced with an aftermarket all-aluminium unit.

4. 4

   Ask specifically whether any transmission work has been performed.

5. 5

   If a workshop inspection is possible: Remove the radiator cap when cold and check the filler neck underside for greasy residue.

Parts involved: Radiator.

$5,000 to $12,000 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 original radiator been replaced with an all-aluminium unit?”
• “Has the ATF ever shown any discolouration or been the subject of a flush?”
• “Has any transmission rebuild or replacement been carried out?”

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.