Toyota’s ongoing V6 engine troubles continue to perplex engineers and owners alike. A third teardown of a failed V35A V6 engine from a Tundra pickup truck has finally provided some fresh clues about what may be causing these powerplants to fail, though the full picture remains incomplete. For potential Tundra buyers, understanding what researchers have discovered so far is essential before making your purchase decision.
What the Latest Teardown Uncovered
A popular YouTube channel dedicated to automotive teardowns recently completed its third examination of a failed V35A V6 engine, and this one proved different from the previous two. The earlier engines showed unmistakable debris scattered throughout the oil system, suggesting severe internal contamination. This third engine, however, presented a subtly different failure mode that may point toward an overheating or cooling system root cause.
When the technician began disassembly, cooling system deposits became immediately visible. The water pump was heavily encrusted with mineral buildup and corrosion byproducts. As more cooling passages were exposed, this pattern persisted throughout the system. While early internal inspection didn’t reveal catastrophic self-destruction, signs of abnormal wear began surfacing once the camshaft area was examined. The real breakthrough came when the cylinder head was removed.
Head Warping and Coolant Intrusion Point to a Pattern
The cylinder head showed clear resistance during bolt removal, with one bolt seized badly enough to snap a socket. More telling were the coolant stains visible around the gasket sealing surfaces. A precision straightedge test confirmed what the technician suspected: the head was warped. This deformation represents a classic sign of thermal stress from overheating.
Once the oil pan came off, both coolant contamination and metallic debris were visible in the lubricating oil, suggesting coolant was leaking into areas where it had no business being. When the crankshaft was finally exposed, it appeared relatively clean compared to the first two failed engines examined, though bearing wear patterns showed unusual unevenness across multiple thrust bearings.
This particular finding matters greatly for Tundra shoppers. Engine testing and analysis continue to reveal troubling patterns that buyers should monitor closely. A warped head combined with coolant in the oil system points toward a thermal management failure rather than purely manufacturing debris, which could indicate a design flaw rather than an isolated contamination issue.
Is Manufacturing Finally Improving?
One encouraging detail emerged during the borescope inspection of the oil galleries. Unlike the earlier failed engine, which showed massive machining burrs left over from manufacturing, this engine’s passages appeared significantly cleaner. This raised the possibility that Toyota might have corrected its machining processes.
However, the timeline raises new concerns. This problematic engine came from a 2025 model year Tundra, while the catastrophically failed engine examined previously came from a 2026 model. If manufacturing issues were resolved, one would expect the newer model to be cleaner, not the older one. This suggests that whatever is causing these failures may not be a simple manufacturing defect that gets better over time.
What This Means for Tundra Buyers Right Now
The reality is sobering: even after three detailed teardowns, researchers still lack a definitive smoking gun explanation for these engine failures. What they do have is a growing pattern of thermal stress indicators, coolant system problems, and bearing wear that suggests a potential design flaw in how the V35A manages heat or seals its cooling passages.
For shoppers considering a Tundra, this investigation underscores why you should approach any V6-equipped model with caution. Research your specific model year and production date, check Toyota’s service bulletins for any engine work performed, and ask the dealer directly about any recall campaigns or extended warranty coverage for the V6 engine. Understanding the full lineup of newer Tundra options can help you make the best choice for your needs.
The technician behind this investigation has indicated that two additional locked-up V35A engines are scheduled for teardown, and plans to bring in a specialist with deep Toyota V6 knowledge. This ongoing effort may eventually answer the questions that three engines have not yet fully resolved. Until Toyota issues a comprehensive explanation or recall addressing the root cause, prospective buyers should remain vigilant and consider requesting a pre purchase inspection by an independent Toyota specialist before committing to any used Tundra with this engine.
The situation remains fluid, and more answers will likely emerge as additional evidence surfaces. For now, staying informed and asking the right questions is your best defense against potential engine troubles.
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