This has been posted before by moderator salimshah: Lexus Variable valve engines (i.e. the 3.3L VVTi) are interfering and depending on circumstances (relative position of piston and valves as controlled by VVTi) you may or may-not be in interference mode.

The bottom line: you may get lucky and not do any damage, then again, you may be in for an expensive repair.

 

There is no such term in the automotive world called non-Interference mode in engines. Non interference means when either intake or exhaust valves are fully open and the piston is DTC. At no point will the valve head be in any position to where the piston head can be.

As for VVTI causing it. It's not going to happen.

 

I'm adding to this because of a recent timing belt change: the belt looked ok, but bearings in one of the pulleys/tensioners was starting to go. That failure can still cause damage even if the belt is ok, so don't only focus on it.

 

My original timing belt lasted 250,000 kms. Belt was shredded to half the original width, mechanic said he'd never seem anything like it.

Car is now at 280,00 and the belt has broken again.. permanent damage or dodgy install? Water pump is still original.

 

I have a 2004 RX330 with 108,000 miles on it. According to VIN lookup, this car has a 3.3L 3MZ-FE V6 engine. On yourcarangel.com, the 3.3L V6 engine is listed as a non-interference engine. From motorreviewer.com: "The 3MZ engine has aluminum cylinder heads with four valves per cylinders and belt-driven double overhead camshafts. The engine uses a timing belt to drive the exhaust camshafts only and those, in turn, rotate the intake camshafts through gears."

I have read on the forum that if timing belts on non-interference engines break it does not damage the engine. My question is what exactly happens if the timing belt were to break on this car? Is a timing belt less likely to break on a non-interference engine than on an interference engine?

https://vpic.nhtsa.dot.gov/decoder/Decoder
https://yourcarangel.com/2014/07/int...complete-list/
https://www.motorreviewer.com/engine.php?engine_id=150

 

I can positively confirm that the 3.3L 3MZ-FE V6 engine is NOT interference. My daughter was driving the on the highway at FULL speed, about 75MPH, when the timing belt snapped. She pulled to the side of the road and not knowing what was wrong she tried to start the car a few times. I feared the worst.
Later, when the vehicle was towed, I confirmed the timing belt snapped. I prepared myself to remove the heads because I was sure there were valves and possibly piston damage. But before that, I decided to try to install a new timing belt. The first thing I aligned was the crank. The Next step was to align the front CAM with the timing mark, interesting enough I was able to move it with a 17mm socket. The next step was to align the rear CAM. I could also rotate almost a full turn to align it with the mark. I replaced the water pump and installed a new timing belt. Before starting the car I decided to turn the cranck with the new timing belt three full turns to look for signs of obstruction, but I did not feel any. Finally, I started the start and ran smoothly.

 

My RX 330 had a timing belt done a few years ago hy the previous owner at a Lexus Dealership. It shows on the CARFAX but there is no sticker on the car for the service. Should I be concerned?

 

This is good news!
Thank you for posting. 🏆

 

I hope people don't see this and not change their timing belts at reasonable intervals in their VVT-i 3MZ-FE V6 engines. If you look at the Toyota forums, there are people who have had experienced timing belt failure and the result was valve damage.
Anecdotally and I am going way back in time, I had a 1984 Honda Accord and I was passing someone and the timing belt let go. The Honda design was interference, but I got lucky and it didn't do any damage. Had it towed, mechanic checked engine, replaced belt and was good to go and back on the road. I got lucky.

 

Concerned about what? Verify at any Lexus dealership that it was in fact done do not take a previous owners word for it. If concerned put your own sticker on it. have it done again 100k miles after it was last done. As Mentioned earlier you also want to make sure the tensioner pulley bearings were replaced as well they need to be done with the timing belt