Toyota Engine Teardown Shows What Happens When One Of The World's Most Reliable Engines Goes Bad

Toyota is renowned for reliability, which helps it retain its top spot on the global sales chart, but even the brand's most reliable motors can fail, as the engine teardown video below shows. This 2.5-liter 2AR-FE Toyota engine - sourced from a 2012 Scion tC but also found in cars like the Camry and RAV4 - somehow met its demise despite looking clean and intact.

Eric, our favorite engine pathologist, conducted a teardown work on the power plant to see what killed it. The first order of business was to see if the crank still turns. It exhibited minimal rotation, suggesting the damage could be found in the crankshaft assembly. That's still a long way to go, but he didn't waste time and started removing the manifolds.

Upon inspection, there was dust, spider webs, moisture, and dirt in the intake and exhaust ports, hinting water could've infiltrated the power unit. The oil filter looked good, though, and no metal scraps were seen between the filter media normally found in a beat-up engine.

Eric then removed the valve cover, and to his surprise, the assembly looked new. He said it is one of the cleanest engines he's seen in a while, a breath of fresh after tearing down a flooded and rusted LS1 V8 from a Chevrolet Camaro weeks ago. The next was the timing assembly; its components appeared in good condition.

With that out of the way, Eric got a hold of the cam assembly. He described the camshafts to be in perfect condition. The rocker arms connected to the camshafts look just fine as well.

He eventually discovers the death of this engine may have been caused by a faulty component in the crankshaft assembly.

After removing the cylinder head, he discovered rust in the cylinders themselves, along with incorrect piston positioning. Cylinders one, two, and three were at the bottom of their strokes, and cylinder four at the top. A further investigation revealed chunks of metal in the oil pan, and after removing the crankshaft, Eric saw a broken connecting rod and several impact marks in the cylinder wall.

Eric concluded the engine failed because of hydrolock, a condition where water enters the engine. Since liquid is incompressible, when the piston tries to engage its compression stroke, the next weakest link buckles, which in this case is the conrod.

Not even legendary Toyota reliability can withstand hydrolocking, and it's a lesson we've learned before with a 4Runner as to why water and engines do not mix.