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Jumped Timing Chain - broke all intake valves - need whole new engine

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#21 ·
ravenuer said:
Go to Toyota . com/owners, register(maybe), input the vin and any work done by any Toyota dealer anywhere will be in the maintenance records.
I wouldn't rely on Carfax. I once looked up a Subaru I bought new and found it was in an accident in a state I've never visited!
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Amazing - appears that fraud was committed by someone in selling a vehicle as new when it had been in a crash - in another state or anywhere!
 
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#22 · (Edited)
Like fishexpo said, if an interference engine jumps timing valve damage is certain and instantaneous. The real issue is how much collateral damage is done -- to the valve lifters and camshaft, or cracked pistons, or even piston rod bearings. You really can't tell without a whole engine tear down. I'd be looking for a used engine from a reliable wrecking yard -- you can usually get some short warranty on it from a good wrecker.
And it would be interesting to learn the root cause -- whether the chain tensioner failed or VVT. There was a little info on the oil line to the VVT leaking, but I think that was on V6 engines.
 
#23 ·
If I were visiting a wrecker, I'd be looking into upgrading to the 3.5 with 5-speed. I don't know how much work would be involved though. Probably a V6 ECU at a minimum.
 
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#25 ·
ravenuer said:
I seem to recall that question on here a while ago. IIRC, the short answer was forget about it.
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Yep, The slightly less short answer was sell the I4 and buy a V6.
 
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#26 ·
fishexpo101 said:
The 2.5L 2AR-FE in the Rav4 is an interference type engine.

I've owned and worked on the 1.8L 1ZZ-FE, 1.8L 2ZZ-GE, 2.4L 2AZ-FE, and the 2.5L 2AR-FE - all are chain drive, variable valve timed engines (all but the 2AR-FE, have single VVT-I on the intake side). The 2ZZ-GE added a two stage life in addition to the variable valve timing (VVTL-I).

Cannot tell just by looking at the exterior of the engine - and unfortunately, most publications may not have the correct or are missing information. Even the Toyota Factory Service manuals are not without typos (wrong torque values, clearance tolerance, etc) - that's why there are number of addendums that came out to address these issues.

Best to confirm with a manual test, as mentioned above. With the timing chain off - rotate the camshafts to full extend a set of valves - then rotate the crankshaft. The piston will make contact with the extended valve. That is pretty much the definition of interference engines. Visual inspection of the valve and piston tops will also confirm if it was an interference issue - as the damage will be unique compared to other catastrophic engine damage.

So in the event of catastrophic timing chain damage (chain broke, jumped a tooth on the sprocket, etc.) - you will end up damaging some of the valves. Even in non-interference engines, you could still see some valvetrain damage if the there was some foreign matter that got into the cylinder (valve actually got sucked in, broken bits of piston, hydrolock, etc.).

That said - the likelihood of the timing jumping a tooth like that is exceptionally rare. Even in the cases of excessive oil consumption with the 1ZZ-FE engines in the 8th generation Corolla/Prisms and the 2AZ-FE corporate engine used in a number of Toyota and Scion vehicles - most of those succumbed to cylinder wall damage or piston ring-land damage (loss of compression) before it lost timing.

I'd be very interested to hear if the timing chain tensioner had anything to do with the timing jumping a tooth or if there was an issue with the VVT actuator and connected sprocket. Chain failure is pretty remote, even in extreme cases with loss of lubrication - but that timing chain tensioner is known to be leak oil due to that single o-ring setup and being an oil fed plunger. Some of the previous generation 2.4L engines had sprocket damage, possibly due to a materials issue - but since they were also ran low on oil, they exceeded the lubrication limit and excessive wear really set in.
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Apologies for reviving this old thread but the folks here seem very knowledgeable and the topic very relevant to my situation.

My 2010 Rav4 Sport (4 cylinder, 195000 km) started experiencing poor acceleration suddenly one day while driving and after that day it usually takes a couple tries each time starting the car. Other than poor power, it seems to drive and sound ok. I looked all over the internet and everything pointed to a timing chain issue.

I brought it to a mechanic and left it with them to diagnose. Later, they said they confirmed that the timing chain was off by 1 tooth but they don't think anything else is broken. It was a smaller shop and they said they brought in outside help who had some sort of expensive computer equipment that can diagnose these things ("electrically", not physically, they never opened up the engine). Not talking about an OBD2 reader here as we already did that and the reader was showing camshaft / crankshaft position sensor codes. I'm only guessing here, but I'm thinking their equipment probably showed the relative positions of the various shafts to confirm they were out of sync.

They said there are 2 options to fix it:
1) Replace the timing chain along with with tensioner, guides, water pump, etc (Canadian ~$3000, high level quote)
2) Replace the engine with a working used engine ($3500 high level quote, depending on what age/mileage of used engine they can find)

The part that puzzles me is that they said this 2010 Rav4 2.5L engine requires the whole engine to be removed to replace the timing chain due to space constraints, therefore making the timing chain replacement very expensive. They mentioned if it was the older 2.4L engine then they wouldn't need to remove the engine to replace the timing chain.

Is it true that the 2.5L engine needs to be removed completely to replace the timing chain?
Any advice on whether to just do the chain replacement vs replacing the entire engine?
Thank you all in advance!
 
#27 ·
If at all possible I'd get a second opinion and I'd think a compression test would confirm the issue. Removing the valve cover and checking for cam split overlap at TDC would be conclusive too. (Edit: VVT may throw that off.)
I don't know about pulling the engine to change the chain & components but I'm sure Toyota didn't leave any extra room since a chain change isn't a normal procedure like a belt replacement would be.
If there are no other issues I'd keep the original engine unless you can get a verified low mileage replacement.
 
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#28 ·
Am no expert about this but I seem to recall from this forum that there are marks on camshaft and crankshaft chain drive gears to indicate the proper relationship between them.
 
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#29 ·
Blogson said:
Am no expert about this but I seem to recall from this forum that there are marks on camshaft and crankshaft chain drive gears to indicate the proper relationship between them.
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Yes that's the only way to absolutely confirm a jump but it likely requires a lot of work to be able to see the marks.
 
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#30 ·
Thank you both for your input!
A few follow up questions if you don't mind.

1) Any hypothesis on how the 1 tooth chain skip could have happened? The mechanic said if oil levels are low then the chain tensioner might have been loose enough for the chain to skip. But the oil levels were fine and the oil was actually changed just a month or so prior to this happening. Chain tensioner stuck/failed? Just a freak accident? Or is there anything else in the engine that might somehow cause the chain to skip even if the tensioner was fine (and possibly cause this again after replacing the chain and tensioner)?

2) How would we check if there's any other issues with the engine? The mechanic said it's okay and it sounds like that's the case because no alarming sounds and the chain is only off by 1 tooth. Is a 1 tooth off timing chain enough to cause interference damage to the valves or anything else in the engine?

3) What would be the downsides if I kept driving the car around with the 1 tooth off timing chain (staying on local roads and avoiding highways due to the weak acceleration)? I'm assuming the worst that can happen to the car is the timing chain skips more teeth and destroys the valves because it's an interference engine. Then the engine would need to be replaced (or rebuilt) but that's pretty much where I'm at now already based on cost.
 
#31 ·
1) w/o any oil pressure issues about the only way the chain, assuming it isn't defective, could jump is if one of the guides broke or failed. Harley had that issue on its early Twin Cam engines ten years ago but those engines get beat on much harder than car ones.
IMO if there was enough slack due to failed guides a good mechanic could feel some play in the chain as he moved the crankshaft pulley.

2) I doubt one tooth would cause valve contact, low compression certainly but any bent valves would register almost zero compression.
Along that line I once did a test on my '78 Honda Accord years ago. I purposely ran it with the timing belt advanced and then retarded one tooth. One way it had very little power until it got revved up and the other way it had immediate power right off idle but quickly fell off at higher revs.

#3 sounds to me like a reasonable option and if it jumps more you won't be concerned with #2 because there WILL be other issues.
 
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#32 ·
Thank you for your input, it's been tremendously helpful!

Do you think it's a possibility to move the timing chain back a tooth over just by opening the valve cover? Like stick something down there to retract the tensioner and then work the chain across the sprockets from the top (probably taking the top chain guide off too).

The mechanic seemed pretty confident it was off by 1 tooth only but would they be able to confirm the alignments with just the valve cover off and looking? Or there would still be some guesswork with which direction the chain is off by?
 
#33 ·
Obviously I don't know for sure but IMO one should be able to check the cam timing and also see how loose the chain is by taking the valve cover off.
As for forcing the chain back a tooth that sounds like a destructive procedure bound to break, or more accurately, finish breaking something.
 
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#34 ·
After doing more internet research, I found answers to a couple of my previous questions in this thread below. Thought I'd share my findings here in case anyone was wondering.
DIY: T-SB-0041-13 Cold Start Death Rattle 2AR-FE (2.5L)...

1) It is possible to get enough slack to adjust the timing chain from above by opening the valve cover (without removing the front cover). The timing chain tensioner can be removed by opening a small tensioner cover plate accessed through the front passenger wheel well. Described in post #1 of the linked thread.

2) It is possible to remove the front cover to do the timing chain replacement without having to pull the whole engine. Described in posts #27, #37, #40, and #41 of the linked thread.

Still not quite sure what I'll do yet but at least this gives me hope that it won't cost as much as the original estimates.
 
#37 ·
Do not buy Toyotas with 2.5L 4 cylinder engine AWG. I had the engine fail the same way. My 2015 had 85k miles and was well taken cared of. Time chain failed with no noise. I think this engine model should have not been put in a Rav 4.
 
#38 ·
Cartech said:
Do not buy Toyotas with 2.5L 4 cylinder engine AWG. I had the engine fail the same way. My 2015 had 85k miles and was well taken cared of. Time chain failed with no noise. I think this engine model should have not been put in a Rav 4.
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This is not a common failure and just because you had a problem does not mean it is a bad engine.
 
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