Toyota Harrier: 1MZ-FE Rear Cylinder Bank Head Gasket Seepage

The rear cylinder bank (bank 2) head gasket on the 1MZ-FE is known to develop external coolant seepage and, in more advanced cases, combustion gas ingress into the cooling system. The V6 transverse mounting means the rear bank is deeply recessed against the firewall, making early seepage invisible during routine inspection. Coolant loss without any visible puddle under the car is the most common presentation. The fault is compounded by the sludge problem: degraded oil quality accelerates head gasket deterioration. Workshop manuals confirm the rear head gasket is a scheduled replacement item in high-mileage service documentation for this engine.

• Gradual coolant loss with no puddle found on the ground and no visible external leak
• White or sweet-smelling exhaust smoke on startup, particularly when cold
• Coolant reservoir showing oily film or brownish discolouration
• Heater output fluctuating or declining due to air pockets in the cooling system

1. 1

   Check the coolant reservoir level and look for oil contamination or brownish tint.

2. 2

   Use a combustion leak tester (block tester with blue fluid) on the radiator filler neck with the engine warm — colour change to yellow or green confirms exhaust gases in coolant.

3. 3

   Inspect the firewall-side of the engine for coolant staining or dried white residue on the block.

4. 4

   Check the oil filler cap underside for cream-coloured emulsification.

Parts involved: Head gasket.

$1,800 to $3,800 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.

• “Has the cooling system ever been pressure tested or the coolant renewed in the last two years?”
• “Has the vehicle ever overheated or needed coolant top-ups between services?”
• “Has a combustion leak test been performed on the cooling system?”

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.