Thanks to Critic

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Hi-I have a 2012 Prius V-bought it about two years ago-drive a lot have like 231 on it now. Last week heard this godawful sound… went to this private shop and he wasn’t around… went to Monro-which they always have a space opened to check out the car… well guy did scan with a little handheld scan… said cylinder one misfiring… had plugs with me and got them changed with one ignition coil… still had hesitation and weird sound… went back and guy said just drive it around for a couple of days-and come back if there is a problem… said was likely unburnt fuel… well ended up up going to Prius chats and saw Critic’s post on there that mentioned and described blown head gasket. Was able to take it next morning to shop that sold this Prius to the guy I bought car from and they just work on Priuses. They did head gasket and water pump with oil change for 2500… they checked egr said looked clean… there mechanic was going on vacation on Monday and figured can maybe get that cleaned thoroughly when they or another place may have more time…took it in Thursday at 11 am and got car back on Saturday at 1130am. didnt want to tell them to do it when they said looked “pretty good.” If I didn’t see Critic’s posting on Prius chat and saw a YouTube video which may or may not have been from critic as well -I likely would have driven it until head warped and would have needed a new engine… just wanted to say thank you to Critic for his contributions here and also on Prius Chat, which was helpful in describing and showing exact symptoms Prius has when head gasket is blown.
 
@The Critic brings invaluable expertise to the forum

Glad you got ahead of the situation before it got more expensive👍

Has anyone found out why these engines (2ZR-FXE) blow head gaskets?
The normal 2ZR-FE in Corolla/Matrix/Vibe/xD don't seem to blow head gaskets as notably?

  • Coolant hot spots?
  • Pre detonation/pinging?
  • Frequent starting without full warmup?
  • Poor clamping forces (ARP studs maybe 🤔)?
All hypothetical of course, anyone?
 
... Has anyone found out why these engines (2ZR-FXE) blow head gaskets?
The normal 2ZR-FE in Corolla/Matrix/Vibe/xD don't seem to blow head gaskets as notably? ...
Popular hypotheses include
1. More frequent and wider thermal cycling than on Corolla et al.;
2. Carbon clogging of EGR cooler, and uneven clogging of intake manifold EGR passages
3. Excessive oil consumption on some 2010-2013 examples, which aggravates #2 above.

Toyota made several improvements which (at least mostly) eliminated the problem in later (4th-generation Prii) 2ZR-FXE engines.
 
Popular hypotheses include
1. More frequent and wider thermal cycling than on Corolla et al.;
2. Carbon clogging of EGR cooler, and uneven clogging of intake manifold EGR passages
3. Excessive oil consumption on some 2010-2013 examples, which aggravates #2 above.

Toyota made several improvements which (at least mostly) eliminated the problem in later (4th-generation Prii) 2ZR-FXE engines.
Thank you for posting that… ai specifically asked place had work done to clean the egr system…. They said it looked good and didn’t recommend it…I texted the place on Thursday morning after reading up on various Prius Posts-and Critic’s posts and description of the problem-initially said would bring car in on Monday since off President’s day and gal said their mechanic who does head gaskets was going on vacation that day, but if I brought it to them that morning they would have it done beforehand… wondered if there was a bit of time pressure on their part that contributed to the recommendation not to clean egr system…and I had gal double check with the mechanic and he said looked good… I change the oil regularly at 5000 miles and person who owned it before was incredibly OCD and really honest… and he also changed oil regularly and would add maybe a half quart-quart between oil changes…vehicle also has 231000 miles… I bought it with 165 on it and this has been the first expensive fix have needed to do… was leaking oil at one point when car was parked and noticed immediately and had oil pressure sender-I think that is what it was-replaced and that fixed that problem… Haven’t had a car make it past 250-had 2011 TDI golf with about 250 that had every light in dashboard lit up-but was able to drive it to get paid for emissions deal… had a 93 Mercedes diesel that had transmission go about 250 and last car was a 2000 Lexus that had numerous issues at about 250 and would have been cost prohibitive to fix… trying to get this vehicle past that “glass ceiling” of 250 thousand miles… I have been on this site for many years and while still not mechanically inclined… and still lack True understanding of most topics… it has given me more confidence to question mechanics and actively look up information… when I told initial Monro Guy who told me to drive for a few days to burn off fuel.. and I told him I think it might be more serious and planned to look at Prius website chats… he kind of patronizingly said : “that is not beneficial-it’s like trying it diagnose a medical problem in web md..”
Well I did go back to him and showed him that had head gasket replaced and simply said to him that… I noticed the mechanic who replaced spark plugs and one ignition coil didn’t test drive the car… and understood you were busy but it would be better to actually drive the car as opposed to telling a customer to drive around for a few days as likely would have warped the head and needed a new engine. am hoping this isn’t the beginning of the end for the vehicle as I have been so fixated on what kind of battery would need to get if that goes-the head gasket and the brake actuator system are just as if not more expensive and happen more frequently… the brake actuator deal seems to be about a 3000 fix… did have brake fluid changed last year… but I think it’s more if something just cracks on that system, which cause a major failure… thanks again for the replies and another thank you to Critic because I think anyone who had similar problem on different posts in Prius chat and were speculating about minor issues… he have the solemn unwanted truth that it was likely the head gasket… have driven car about 200 miles since getting it back on Saturday and knock on wood it is running well…
Would recommend Sam’s Auto near Lancaster Pa for Prius fixes… they also sell tons of used ones on lot but they are overpriced I think… but overall thought they were fair with pricing… had a loaner car immediately when got there Thursday morning and enabled me to go into work that afternoon…
 
Popular hypotheses include
1. ...
2. ..., and uneven clogging of intake manifold EGR passages
3. ...
...
To elaborate on my previous #2 a little bit ... The engine tuning depends on EGR to suppress knocking in under certain conditions. If EGR passages in the manifold to one or two cylinders are clogged, knocking can occur in those cylinders, resulting in abnormally high cylinder pressure. At the same time, the remaining cylinders receive all the EGR flow that was intended for all 4 cylinders, causing them to misfire from excessive EGR.
Periodically cleaning out the manifold EGR passages is good maintenance---and ignored by Toyota's maintenance schedule
At least that's one theory.
 
To elaborate on my previous #2 a little bit ... The engine tuning depends on EGR to suppress knocking in under certain conditions. If EGR passages in the manifold to one or two cylinders are clogged, knocking can occur in those cylinders, resulting in abnormally high cylinder pressure. At the same time, the remaining cylinders receive all the EGR flow that was intended for all 4 cylinders, causing them to misfire from excessive EGR.
Periodically cleaning out the manifold EGR passages is good maintenance---and ignored by Toyota's maintenance schedule
At least that's one theory.
I don't buy that one. The failed HG's I've seen, including my own, had spots on the gasket that were worn.
 
That aligns with the alternate theory of thermal cycling and uneven temperatures being primary culprit.

Does the head gasket fail around a specific cylinder? The clogged EGR port theory might have some credence as that cylinder would run hotter, because EGR cools the intake charge.

Other than that it would have no effect on other cylinders. EGR flow is dictated by the intake stroke of the piston, it doesn’t flow all at once to all cylinders. So blocking one port will not send more exhaust gases to the other cylinders.
 
I don't buy that one. The failed HG's I've seen, including my own, had spots on the gasket that were worn.
Would an old "italian tune-up" help and keep anything from carboning up especially if the engine is operated in the city and sees a very narrow RPM range.
 
Not always. #1 and #2 seem to be more common than the others, but it can happen on any.
And the #1 EGR port seems to be the one most often clogged.

Would an old "italian tune-up" help and keep anything from carboning up especially if the engine is operated in the city and sees a very narrow RPM range.
Nobody knows, but I doubt it. The EGR cooler is cooled by engine coolant, so it would be hard to burn out carbon accumulated there that way, much less farther downstream in the manifold.
 
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