Toyota Yaris: G16E-GTS Cylinder Head Coolant Bridge Crack

The G16E-GTS 1.6T engine's cylinder head contains an internal coolant crossover bridge/gallery cast into the head that is prone to cracking under sustained thermal cycling and high-load operation. When the bridge fails, coolant migrates into the intake ports or combustion chambers, risking hydrolock or catastrophic overheating. Toyota acknowledged the defect and issued a Technical Service Bulletin requiring cylinder head inspection and replacement on affected units.

• Unexplained coolant loss with no visible external leak
• White or grey smoke from exhaust indicating coolant burning in combustion chamber
• Milky or emulsified oil on dipstick or under oil filler cap
• Coolant residue or crystalline deposits visible inside intake manifold
• Engine overheating warning light illuminating under normal conditions

1. 1

   Check coolant reservoir for oily contamination and the oil dipstick and filler cap underside for milky emulsified oil.

2. 2

   Inspect inside the intake manifold for white crystalline residue indicating dried coolant.

3. 3

   Request Toyota dealer service records confirming cylinder head TSB inspection or replacement was completed.

Parts involved: Cylinder head.

≈A$4,140 to ≈A$8,740 at independent workshop rates, shown as an approximate guide in Australian dollars. That is for this job on its own, not for the car.

An estimate, converted to Australian dollars, 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 cylinder head been inspected or replaced under the Toyota TSB for the G16E-GTS coolant bridge crack?”
• “Has the car ever experienced a coolant loss event, low coolant warning, or overheating light?”
• “Can you provide Toyota dealer documentation of any warranty or recall work performed on the engine head?”

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.