Toyota Harrier: 1MZ-FE radiator plastic end tank cracking

The MCU15 Harrier (and Lexus RX300) uses a cross-flow aluminium core radiator with injection-moulded nylon-reinforced plastic end tanks crimped to the core with aluminium headers. After 15 or more years of thermal cycling between cold soak and 90°C operating temperature, the plastic end tanks develop stress cracks at the crimped joint and around the coolant hose inlet/outlet connections. Coolant loss follows, initially minor seeping that the overflow reservoir compensates for, then accelerating to visible dripping or rapid loss. Critically, these radiators also contain an integrated automatic transmission fluid cooler. If the end tank fails on the ATF cooler side and coolant pressure drops, coolant can enter the ATF circuit, causing the distinctive pink-milkshake ATF contamination that destroys the transmission if undetected.

• Coolant loss requiring regular top-up with no visible external leak when cold
• Coolant drips or puddle under front of vehicle after shutdown
• Overheating or temperature gauge climbing higher than normal
• Pink or foamy appearance of automatic transmission fluid on dipstick
• Visible crack or seepage at radiator end tank to core joint

1. 1

   Inspect both plastic end tanks for hairline cracks, particularly at the crimp seam and around hose connections.

2. 2

   Pull the ATF dipstick and check for any pink milky or foamy appearance indicating coolant contamination.

3. 3

   Check overflow reservoir level — if consistently low it indicates a slow leak.

4. 4

   With engine cold, pressurize the cooling system and inspect radiator end tanks for seepage.

5. 5

   Note: if ATF is contaminated, radiator and transmission service are both mandatory.

Parts involved: Radiator.

$550 to $1,900 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 radiator or cooling system ever needed attention or repair?”
• “Has the coolant level ever dropped unexpectedly?”
• “When was the automatic transmission fluid last changed and was it normal colour?”
• “Has the vehicle ever overheated or shown a high temperature warning?”

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.