interference versus noninterference engine??

i wonder if the service manual would have the answer.

 

It has a chain, can we take that as a given, lol.

Blown Head gasket rebuild....@297k | Page 3 | PriusChat

 

With all current systems of mechanically driven valves that I've heard about, a timing belt/chain/gear is essential. This may go away some time in the future when all-electric valves come into play, but that has not yet happened.

 

This is what engine is currently being used in the 4th generation Prius. Being it isn't a 7AFE, 4AFE, or 4AF, that tells me that it is an interfering engine.

#1 in Easley,SC

 

Whether or not it is an interference engine is almost a moot question due to the great reliability of the timing chain. I won't worry about mine. In any case, what are you going to do?...renew the chain every, what?, 200,000 engine miles or so? That would be about 500,000 miles on our Prime. We won't live that long. Neither will the Prime.

I had a 2001 Tundra 4.7 V8 with one of Toyota's very few belt equipped interference engines. Every 90k that engine got a new timing belt. Long ago I had an old Chev V8 where one side plate of one link came loose and was banging the cover until I replaced the chain. But, that was long, long ago, and it was a Chevy.

 

This isn't the first time this question's gone around PriusChat ... the last time I remember seeing it, there was someone reporting a pattern with Toyota engine designs: the non-interference models use belts, the interference designs use chains. I don't remember who said that or on what authority, but it did seem to make a bit of sense.

-Chap

 

I wonder what you would consider to "answer the question as related to this thread"?

You included a list a couple of posts up:

You bolded the line for 7AFE, 4AFE, and 4AF—all engines the Prius doesn't have. The Prius has a 2ZR, which is not mentioned by name in that list, but it is a 1.8L DOHC Gasoline engine, which matches the line above the one you bolded. You mention a 2003 Highlander engine being non-interference, but not which available 2003 Highlander engine you knew that about. I assume you may have meant the 1MZ 3.0L, because the 3MZ 3.3L is shown in your list as an interference design. 3MZ does have VVT-i, and this article claims the engines were non-interference "before the 1999-2003 introduction of VVTI") The 2ZR engine in the Prime also has VVT-i.

To get the closest to a positive answer to your question, you might sign into techinfo.toyota.com and look through the engine mechanical section for the model year of Prime that interests you. You would be looking for telltale instructions like these:


Those are from the 1st generation Prius, 1NZ engine manual, just to give you the drift. They don't want you ever to rotate the crank when the cams won't rotate with it—except in rules 2 and 3, where you are to rotate the crank 40° backwards (enough to move all pistons away from TDC) before you turn any cams ... and, when it's time to undo that, make sure the cams are back in matchmarked position first, then rotate the crank back where it belongs.

That was in the valve-clearance adjustment section for 1NZ. I'm not sure you'll find a valve-clearance adjustment section for 2NZ given that it has hydraulic adjusters. But you might look through the various other sections having to do with cam or head removal, etc. If you find instructions like that, you'll pretty much have your answer.

-Chap

 

What would you consider verification, beyond what is already in this thread? If that isn't enough for you, there will probably be no verification short of you going to the repair manual and looking for a specific passage like the 1NZ passage I quoted above.

-Chap

 

Hope it helps what exactly ??

I think you just have an un-natural obsession with this interference question.

You already found out that it has a chain, not a belt.
AND that the chain is likely to last just as long as other mechanical parts inside the engine.
So.....what difference do you think that it really makes to you; what practical difference, that is ???

 

don't take it personally ed, we're all under the same scrutiny.

 

If a timing chain does break, there will be much damage to both the crankshaft and camshaft gears that the chain connects. Both will probably have to be replaced. The possibility exists that the cam and the crank could also be damaged as well as the bearings on which they ride.

 

Interesting, the timing chain is under $150 here:

Timing Chain for 2015 Toyota Prius|13506-0T020 : Toyota Online Parts | Genuine Toyota parts | Toyota Parts Online | Toyota Parts

And members here are have reported a reseal of the timing cover set them back around $1700.

I would let it be, don't anger it, lol.

 

If a timing chain break is a concern, have it inspected regularly. Broken bits of metal getting tossed around are going to do other damage, that will likely make whether the engine is interference of not moot.

Some parts are just a real PITA to work on or simply get too. Heard you actually have to lift the engine up some to reach the spark plugs on the 6 cylinder Outback.

 

You could search the forums here for other things people have been told by Toyota service managers and senior tech guys about other subjects, and it might not leave you thinking that settles your question either.

Your profile lists "other non-hybrid," so I take it you are asking this question while deciding whether to buy a Prime?

So suppose the senior tech guy tells you "yup, it's an interference engine, just like folks were telling you on PriusChat." What's your next step? Would you buy a different vehicle?

Or, suppose you get a senior tech guy who says, "don't worry, it's a non-interference engine, those PriusChat folks don't know what they're talking about." What's your next step then? Would you buy the Prime?

-Chap