lou95gts

Well, my mothers 2005 Lexus RX330 had a timing belt replacement done at the local Lexus dealer by the former owner at the proper interval. They changed everything except the water pump. 25K Miles later...guess what? The water pump bearing lets go and the timing belt loses tension and skips a dozen or more teeth at highway speed. For sure I thought it would need a motor since it must have made piston and valve contact.
NO! Installed a new belt kit WITH a new water pump and it purrs like a little kitten again. No damage!
I told my mom to go and buy a few lottery tickets.

FYI, My mom complained to my dad that the engine sounded like a coffee grinder for the last few weeks. He told her not to worry about it.

alchemist

iTrader: (1)

That is lucky...how many miles on car when belt was changed by dealer?

maximizese

Good news to hear. You have to love non-interference engines:

http://www.agcoauto.com/content/List...erence_Engines

lou95gts

The belt was done at 100k. Now has 125k.
There is lots of Internet "advice" that this is an interference engine but this event proved that false.

alchemist

iTrader: (1)

I would argue that our engines are interfering at certain conditions

https://www.clublexus.com/forums/rx-...erference.html

hypervish

+1, they are indeed interference engines.

cdnewton

A friend of mine is a Master Toyota tech and I have asked him about this in the past. He said the 3.3L with VVT-i is an interference design.

Having said that, I had a 1984 Honda Accord that had a known issue with a timing belt and if it broke, it was supposed to be a valve bender ... I was passing someone and the timing belt let go <quite scary by the way>. I had it towed to a Honda specialist, he put on a new belt and I was back on the road -- no damage ... I got lucky as did the OP.

lou95gts

This is exactly the "advice" I was referring to. There is no official yes/no from Lexus/Toyota that labels this engine is interference or not.
My first hand experience says it is not but I would still change the timing belt and all related components at the required intervals

smassey321

When the belt jumped a tooth did the check engine light come on?

lou95gts

It jumped about a dozen or more teeth and shut down. The TB lost all tension as the water pump bearing failed completely.

roadbike56

Someone could volunteer to test the theory and let their belt break and find out if it's an interference engine. Any takers?

lexus997

Other factors that indicate an interference engine:

* compression ratio
* recommended fuel octane number


More compression needs higher octane which should equate to an interference engine.


Just because a timing belt fails and there is no damage, that does not necessarily mean that the engine is not an "interference" engine. Sometimes you just get lucky.


I had an Acura MDX where the timing belt failed and did all kinds of engine damage:

* compression ratio 10:1
* recommended fuel octane: 91

HtownBlue

The 3.3 is not an interference engine. It has the compression ratio and lower end of the Toyota interference engines, but the head and valves are modeled after the 3.0 engine which is NOT an interference engine. The valves will not touch the piston close or open. That is why it is not a true interference engine. I would bet I'm one of about 3-5 people here that have actually removed the head of this engine for what it's worth.

cdnewton

I also checked with my friend that is a Toyota Master Diagnostic Technician/ASE L1 ... he said: "The 3.3 (3MZFE) is in fact, an interference engine. The 3.0 or 1MZFE is not. They are almost identical engines, externally, but bore/stroke is different."

See below for the statement from the service manual:

LeX2K

Did you put a piston at TDC and rotate the cams? That's the only way to prove if there is valve interference or not. I lean towards the engine not being interference myself, people say the VVTi makes it interference but that tech has nothing to do with valve lift.