Lexus 2UR-FSE crankshaft failure, dealer blaming wear

[peace25]

I have a Lexus LS 600h (2UR-FSE engine). In July 2025 , a Lexus Main Dealer replaced the timing tensioners and inspected the chain (a major teardown). 10,000 miles later, the engine suffered a catastrophic timing jump, April 13 2026

The Current Situation:

The engine is now dismantled at the same dealership. They are claiming the cause is a "worn sprocket" (wear and tear) and are refusing liability.

The Evidence (See Photos/Video):

The crankshaft keyway is "walloped" and heavily deformed (oval-shaped).

There is significant fretting/galling on the nose of the crankshaft and the mating surfaces of the sprocket.

The sprocket teeth actually look relatively normal for the mileage; the "carnage" is at the center mounting point.

The Theory:

I suspect that during the July repair, the main crankshaft pulley bolt was either under-torqued or reused (if it's a stretch bolt), leading to a loss of clamping force. This allowed the assembly to vibrate/chatter under harmonic load, which eventually destroyed the keyway and caused the timing to jump.

My Questions for the Techs:

In your experience with the UR-series V8s, does a "worn sprocket" ever cause a steel keyway to shear like this?

Does this look like typical "wear and tear," or is this a classic case of a loose crank bolt/failed frictional joint?

Is that main crank bolt a "one-time use" stretch bolt on this engine?

I’m currently in a dispute involving the finance company and an independent inspector. I’d really appreciate any technical "ammunition" or sanity checks you can provide.


Anybody can tell me please how to upload images ? Thanks

[_Rodders_]

Good luck but I doubt you'll get anything out of them even though they probably did cause it.