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

Edited by peace25 on Monday 18th May 18:36

[_Rodders_]

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

[peace25]

_Rodders_ said:

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

So far they are trying to blame the sprocket but after email lexus UK and asking them to have a look once again into all the components they sent me an email said it's possible that lexus branch have caused some damage in the previous work but they can't be certain ...

Now according to the email they sent they are saying the sprocket and crankshaft status are unknown at that time lol, when I checked my invoice , the mechanic notes states that he removed the old timing chain and measured it and refitted back , in this case the sprockets were exposed and while his in there of course he would have examined the crankshaft, the guides and everything else before reverse back everything in place isn't ?

Now Lexus UK is trying to say in another word that they are not responsible for what occur to my car and that I have to deal with Lexus branch directly, waiting this Monday to hear what they will say and if anything didn't move forward , I will get a mechanic inspector down here to give me a report and take it to the court and of course if it's on my favor .

It's bumper I can't upload pictures and video in here but I am.not sure if I have to contact the admins or what ?

Thanks

[stevieturbo]

Get a solicitor, and find a proper workshop/technician who can inspect.

Obviously anything can happen in 10k, but given they were the last people in there.....seems suspicious.

I'd like to know exactly what they did previously, but obviously they're going to try and deny any liability

You're in a bit of a stty position now.

Similar recent one

https://www.youtube.com/watch?v=CqcEI3TlX9A

Although a keyway can never wear if all the fasteners involved around it are tight. So clearly something has came loose. Who was the last person to touch those nuts or bolts ?

Although one case where the nut always came loose from the factory, Z17DTH engine, the cam pulley bolt pretty much always came loose on them unless you undid it, added loctite then re-tightened.
The question was when would it come undone..ironically, often not long after a timing belt change, even though most would never need to touch that nut !

SO strange things can happen, but yours sounds a bit more like a person has caused it, than a common problem

Edited by stevieturbo on Monday 18th May 15:00

[LivLL]

Why on earth would they go to all the trouble of stripping it all down, removing the chain, measuring it and just refitting the same chain?

What mileage was it at when the work was done?

Good luck OP.

[peace25]

stevieturbo said:

Get a solicitor, and find a proper workshop/technician who can inspect.

Obviously anything can happen in 10k, but given they were the last people in there.....seems suspicious.

I'd like to know exactly what they did previously, but obviously they're going to try and deny any liability

You're in a bit of a stty position now.

Similar recent one

https://www.youtube.com/watch?v=CqcEI3TlX9A

Although a keyway can never wear if all the fasteners involved around it are tight. So clearly something has came loose. Who was the last person to touch those nuts or bolts ?

Although one case where the nut always came loose from the factory, Z17DTH engine, the cam pulley bolt pretty much always came loose on them unless you undid it, added loctite then re-tightened.
The question was when would it come undone..ironically, often not long after a timing belt change, even though most would never need to touch that nut !

SO strange things can happen, but yours sounds a bit more like a person has caused it, than a common problem

Edited by stevieturbo on Monday 18th May 15:00

Yes I am in a stty position so far, already planning to get a mechanic inspector up here to investigate as soon as possible before I got ahead with any solicitor. The work is done according to TSB here but at the same time I told them to inspect everything in the timing system while the engine is open including chains , guides and crankshaft sprocket and everything of course which to my invoice the technician did before hand me the car . Now Lexus UK tried to say wear on the sprocket but I took images of the rocket and even a video and all I can see normal wear for the age of the car and no sharp sprocket to cause timing to jump a tooth , I sent lexus UK email myself asking them to reconsider and review again and finally they sent me an email yesterday where lexus is saying this :

Thank you for your patience while we further investigated your concerns.

As advised in my previous email, we shared the images you kindly provided and your correspondence with our internal Technical Team, who have been reviewing the technical case raised by your lexus branch .

Following their review, the Technical Team have advised that it is unfortunately extremely difficult to determine the root cause with certainty. It is possible that some damage may have occurred during the previous repair carried out by the Centre; however, we are unable to conclusively confirm this.

We understand that the Centre replaced the tensioner on the left-hand side only. At that time, the condition of the crankshaft sprockets is unknown, and it is possible there may already have been slight damage present which was unfortunately not identified.

I do sincerely apologise that we are unable to provide a more conclusive diagnosis, however, due to the vehicle having been dismantled and worked on recently, it is impossible to be certain.

I appreciate this is not the definitive outcome you were hoping for, and I apologise again that we are unable to provide a more certain conclusion.

With regard to your request for assistance with the loan vehicle costs, as the vehicle hire has been arranged directly through your lexus branch, any discussions relating to these charges, or concerns regarding the previous repair carried out by the Centre, would need to be raised directly with your lexus branch .

My reply as follow :

Thank you for the update and for looking into this with the Technical Team.

I appreciate the apology and the transparency regarding the difficulty in determining the root cause. It s a lot of information to take in, especially with the team acknowledging that the damage may have (possibly) originated during the previous repair at the Centre.

However, I noticed you mentioned that the condition of the crankshaft sprockets was "unknown" during the July repair. I have the invoice from that visit (Ref: LAB 23.00), and the technician's notes state:
"Stripped engine front end and removed chains, measured chains all ok refitted chains with new left hand tensioner and refitted everything..."

Since the front of the engine was stripped and the chains were removed and measured, the sprockets were fully exposed and inspected by the technician at that time. If there had been any damage or wear, it would have been identified before the chains were refitted and the engine was timed.

Given that the system was "OK'ed" and reassembled by a Lexus specialist ( Not a Master Lexus Technician of course ) less than a year ago, it reinforces the point that the current failure is linked to that intervention.

I ll be discussing this directly with my center but I wanted to ensure the technical record was clear regarding what was inspected in July.



That's about it . Today I have received the compression test images and I will post them here .

[peace25]

LivLL said:

Why on earth would they go to all the trouble of stripping it all down, removing the chain, measuring it and just refitting the same chain?

What mileage was it at when the work was done?

Good luck OP.

Tell me about it and I told them to change the chain as well but they never listened ! It was something like 97976 mile and failed at 106k mile .

[peace25]

Test leakage images are they any good result here ? I can see two on yellow , is that concerning ?

Edited by peace25 on Monday 18th May 20:10

[LivLL]

peace25 said:

Test compression images are they any good result here ? I can see two on yellow , is that concerning ?

That's a leakdown tester, not a compression tester. Without knowing how they were using it and how the engine was setup, the pics aren't much use.

[peace25]

LivLL said:

peace25 said:

Test compression images are they any good result here ? I can see two on yellow , is that concerning ?

That's a leakdown tester, not a compression tester. Without knowing how they were using it and how the engine was setup, the pics aren't much use.

So what questions I should ask about the images ?

[LivLL]

I'll leave it there, I see you've asked in various other forums, socials etc.. across the internet.

[peace25]

LivLL said:

I'll leave it there, I see you've asked in various other forums, socials etc.. across the internet.

Yep , the more information I gather , the better 😉 , all I am waiting for now is lexus final approach to this catastrophe ! Once they go difficult , I'll instruct an inspector to come and up and have a look at this mess .

[stevieturbo]

The REPerformance video I linked you, also highlights the stupidity of a static piece of information on a leakdown test, because we've no idea if they are using it correctly.

But it can be fairly simple.

Sprocket wear. Yes, the toothed sprocket can wear from contact with the chain. Not normal, but possible with high miles etc.

Key way deformation. This is in no way normal or possible on an engine where the front pulley bolt is tight that secures it all together. Anyone who says that is normal or just wear, is an absolute f**king idiot.

So who was last at that bolt ? And equally important although I'm sure they won't say. Was it loose or tight when they took things apart recently ?

[peace25]

stevieturbo said:

The REPerformance video I linked you, also highlights the stupidity of a static piece of information on a leakdown test, because we've no idea if they are using it correctly.

But it can be fairly simple.

Sprocket wear. Yes, the toothed sprocket can wear from contact with the chain. Not normal, but possible with high miles etc.

Key way deformation. This is in no way normal or possible on an engine where the front pulley bolt is tight that secures it all together. Anyone who says that is normal or just wear, is an absolute f**king idiot.

So who was last at that bolt ? And equally important although I'm sure they won't say. Was it loose or tight when they took things apart recently ?

Thanks for your reply the last ones are lexus ( Toyota ) mechanic , I don't think they will admit it . They are the last one who was inside the timing and they are the last one who dismantled it for checking so surely they want admit that. Everyone saying same thing , they didn't tighten the bolts of the pulley right or something got slacked off while they were in last time .

[stevieturbo]

peace25 said:

Thanks for your reply the last ones are lexus ( Toyota ) mechanic , I don't think they will admit it . They are the last one who was inside the timing and they are the last one who dismantled it for checking so surely they want admit that. Everyone saying same thing , they didn't tighten the bolts of the pulley right or something got slacked off while they were in last time .

A detailed report of what their previous work was would maybe help, because they will have to admit they undid that pulley bolt if they are claiming they had everything undone to inspect as you say.
Although you do say they replaced the tensioners and inspected the chain, so did they undo that bolt at all ? What is needed to gain access to the tensioners etc ? Just part of a cover, or does the entire thing need opened up ?

Certainly looks like it needs fully opened ?

https://www.youtube.com/watch?v=QnEjU8QtjA8

Often these can be a single use bolt, that is supposed to be replaced. Is this on your bill, and does it look like a new bolt ? Is there supposed to be any thread lock on it ( not usually ) ?

Can they provide any evidence of this being torqued to spec during that previous build ?

Was the key itself replaced at that time ? Not usually a thing...but who knows. Again, any receipts ?

[stevieturbo]

221lbft is a healthy torque, as many crank pulley bolts are these days

https://charm.li/Lexus/2009/LS%20600h%20V8-5.0L%20...

[peace25]

stevieturbo said:

peace25 said:

Thanks for your reply the last ones are lexus ( Toyota ) mechanic , I don't think they will admit it . They are the last one who was inside the timing and they are the last one who dismantled it for checking so surely they want admit that. Everyone saying same thing , they didn't tighten the bolts of the pulley right or something got slacked off while they were in last time .

A detailed report of what their previous work was would maybe help, because they will have to admit they undid that pulley bolt if they are claiming they had everything undone to inspect as you say.
Although you do say they replaced the tensioners and inspected the chain, so did they undo that bolt at all ? What is needed to gain access to the tensioners etc ? Just part of a cover, or does the entire thing need opened up ?

Certainly looks like it needs fully opened ?

https://www.youtube.com/watch?v=QnEjU8QtjA8

Often these can be a single use bolt, that is supposed to be replaced. Is this on your bill, and does it look like a new bolt ? Is there supposed to be any thread lock on it ( not usually ) ?

Can they provide any evidence of this being torqued to spec during that previous build ?

Was the key itself replaced at that time ? Not usually a thing...but who knows. Again, any receipts ?

The bolt can be reused again ! And in my invoice this is what the technician said :

LAB 0.01 0.00 0.00 S
Investigated rattle from engine at cold, suspect
chains, found relevant bulletin stating left had
tensioner faulty and making chain slap
Menu Subtotal: 0.00

---

A LAB 23.00 170.00 3490.79 S
Removed engine and transmission, stripped engine
fron end and removed chains, measured chains all
ok refitted chains with new left hand tensioner
and refitted everything in reverse order,
topped up all fluids and bled coolant preformed
wheel alignment and roadtested all ok
T NOTES 0.00 0.00 0.00 S
Carried out multiple cold starts and confirmed


I asked them to check everything in there and even to order new chain and fit it but they all have done is checked everything including the old chain and removed it and measured it and put it back !

Now Lexus UK told my branch that they (Think ) it's the sprocket worn and cause timing to skip tooth or jump and causes all of this , I have sent an email to lexus UK with my images I took and video and told them to review again and that I am not satisfied with there finding and lexus got back to me with this email :


Thank you for your patience while we further investigated your concerns.

As advised in my previous email, we shared the images you kindly provided and your correspondence with our internal Technical Team, who have been reviewing the technical case raised by your lexus Branch.

Following their review, the Technical Team have advised that it is unfortunately extremely difficult to determine the root cause with certainty. It is possible that some damage may have occurred during the previous repair carried out by the Centre; however, we are unable to conclusively confirm this.

We understand that the Centre replaced the tensioner on the left-hand side only. At that time, the condition of the crankshaft sprockets is unknown, and it is possible there may already have been slight damage present which was unfortunately not identified.

I do sincerely apologise that we are unable to provide a more conclusive diagnosis, however, due to the vehicle having been dismantled and worked on recently, it is impossible to be certain.

I appreciate this is not the definitive outcome you were hoping for, and I apologise again that we are unable to provide a more certain conclusion.

With regard to your request for assistance with the loan vehicle costs, as the vehicle hire has been arranged directly through Lexus branch, any discussions relating to these charges, or concerns regarding the previous repair carried out by the Centre, would need to be raised directly with Lexus branch.



And my reply was as follow :



Thank you for the update and for looking into this with the Technical Team.

I appreciate the apology and the transparency regarding the difficulty in determining the root cause. It’s a lot of information to take in, especially with the team acknowledging that the damage may have (possibly) originated during the previous repair at the Centre.

However, I noticed you mentioned that the condition of the crankshaft sprockets was "unknown" during the July repair. I have the invoice from that visit (Ref: LAB 23.00), and the technician's notes state:
"Stripped engine front end and removed chains, measured chains all ok refitted chains with new left hand tensioner and refitted everything..."

Since the front of the engine was stripped and the chains were removed and measured, the sprockets were fully exposed and inspected by the technician at that time. If there had been any damage or wear, it would have been identified before the chains were refitted and the engine was timed.

Given that the system was "OK'ed" and reassembled by a Lexus specialist ( Not a Master Lexus Technician of course ) less than a year ago, it reinforces the point that the current failure is linked to that intervention.

I’ll be discussing this directly with my centre, but I wanted to ensure the technical record was clear regarding what was inspected in July.





Now if you read well their response they are trying to say it is possibly that the branch have caused this damage ! Also they are trying to be smart by saying Sprocket and shaft health was unknown at that time and my reply was that the branch technician stated clearly that he removed the old timing chain and measured and refitted again and if so means the sprocket were exposed as well must had a look at the shaft and to all the dam component there ,.specially I have told them to check everything before finishing the job while the engine is dismantled !!!! What a joke !!!! Micky Mouse in the house .

[peace25]

stevieturbo said:

221lbft is a healthy torque, as many crank pulley bolts are these days

https://charm.li/Lexus/2009/LS%20600h%20V8-5.0L%20...

Yep

[Tuktuk]

I fully to agree with the others that the wear on the key and keyway are completely abnormal and strongly indicative of the crank pulley bolt not being tightened sufficiently. The key/keyway is purely for alignment during assembly and does not take any load for driving the sprocket when the crank pulley bolt is tightened sufficiently.

[peace25]

Tuktuk said:

I fully to agree with the others that the wear on the key and keyway are completely abnormal and strongly indicative of the crank pulley bolt not being tightened sufficiently. The key/keyway is purely for alignment during assembly and does not take any load for driving the sprocket when the crank pulley bolt is tightened sufficiently.

I think everyone saying the same matey and I totally agree here so probably it's time to get an independent inspection up and running .