2010 Prius with coolant and spark plug issue

Takes a few more words to describe, because 'leaner' and 'richer' have specific meanings that aren't right for talking about EGR.

'Leaner' and 'richer' both refer specifically to the ratio of oxygen to fuel entering the cylinder. There is a stoichiometric or "just right" ratio (the Goldilocks version is easier to say), and a 'lean' mixture is one with too much oxygen for the amount of fuel, and a 'rich' mixture has too much fuel for the amount of air.

The magic with EGR is that exhaust gas is neither oxygen nor fuel—you can let some in and it doesn't make the mixture leaner or richer. The fuel and oxygen are still in Just Right proportions, there's just less of both in the cylinder. The molecules of fuel and oxygen are farther apart, and take longer to find each other; the combustion happens more slowly, releasing the expected amount of energy but spread out over more of the piston travel. That has both emissions and MPG benefits.

The systems do tend to get plugged with soot. The first car with EGR that I personally worked on was a 1979, and I had to ream out those passages once or twice a year. The tech goes back at least several years before that.

 

Clearly flawed engineering design and testing. Not out of spec parts. Low tension rings were used on many models including Camry, Corolla and Rav4s of the era. Many were non hybrids but all had plenty of vehicles with excessive oil consumption. Toyota did not rebuild free after 60,000 miles but most examples present after 100,000. We are talking a quart or more every 1000 miles. Enough to run the engine dry twice between oil changes. Which happens.

Toyota provided many piston and ring rebuilds free within the powertrain warranty to remedy the problem.

 

I’m in agreement with what happened, only saying Toyota went with those rings intentionally.

Too, if the runaway oil consumption commences typically happens past 100k miles, Toyota’s pledge to replace rings with revised ones, but only up until 60k miles, left many owners to shoulder the repair cost, and most would choose less costly (and less satisfactory) options.

I’d suspect many just walked away.

 

And the magic falls apart when that exhaust gas is not delivered; doubly so when it’s not delivered unevenly between the cylinders?

 

That is one of your weaker arguments. Especially when they had to eat the repairs and redesign the parts.

 

I wasn't aware I was arguing, lol. Won't be the first time this has been brought to my attention, so yeah, maybe.

You're saying the original rings had a defect, didn't meet the specs Toyota came up with? And this went on for about 5.5 model years, (they revised, or corrected, the rings, sometime through model year 2014)

I'd speculate very few owners met the criteria for the block rebuild, which was greater than one quart oil consumption per 1100~1300 miles of use, with less than 60K miles on the odometer. (Test criteria attached)

 

Or doubly so when it is delivered unevenly between the cylinders.

 

Ah, double negative got me. Thanks, fixed.

 

The word 'argument' has a couple different meanings:

1. some heated adversarial discussion, or
2. a marshaling of evidence in support of a conclusion or position

The way rj was using it looks more like sense (2). That's the usual kind of 'argument' someone might call 'stronger' or 'weaker', as a judgment of how well the marshaled evidence supports the conclusion. (The other kind of 'argument', someone might call louder, or meaner, or more profane, or whatever.)

So, when you're lining up evidence leading toward some conclusion, you are arguing ... in one of the senses of the word.

 

True that. Musing about words is interesting, kind of like archaeology. Was thinking last night about "vacant". These days it seems to typically apply to real estate status, like "vacant" possession, stuff like that. But looking at my avatar: "vacant" gaze?

Then there's patient patients.

 

“There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know.”

Donald Rumsfeld

 

https://www.allmusic.com/album/the-poetry-of-donald-rumsfeld-and-other-fresh-american-art-songs-mw0000701507

 

You have a ways to go. The timing chain and cover has to come off along with everything connected to it. Then the exhaust and intake manifold and hoses, egr and wiring. Then the
head. Basically you have the valve cover off now.

The head gasket is between the head and the block. At that point damage assessments can take place.

 

The cam cover is next. Then it's EASY to remove the bolts for the exhaust manifold.
Then the intake manifold. Then the timing chain cover.
I wouldn't be surprised if the holes to drain the oil from the head to the oil pan are block,
or mostly blocked.

Some used non synthetic oil, and/or cheap oil. And never changed the oil and/or filter.

 

The way it looks inside is not okay. There is a lot of slug.
The rings are probably all gumed up and the engine likely burns a lot of oil.
The only way to clean it is to take it completely apart and clean each park. A lot of work.
But it doesn't cost a lot. But a risk of the bearings being worn.

And since you've never taken an engine apart, it will be a lot of work and stress for you.
But if you are interesting in doing this type of work, it's a great learning experience.

You can pull the spark plugs and get an inexpensive scope from ebay for $20-30 that will work
with your iPad and you can look at what the cylinder walls look like. If they are not too scored,
you'll probably be okay for many miles.

From what you've described, you almost certainly have a head gasket failure.
Depending on your finacial situation, replace the head gasket (hopefully there isn't any damaging
"stop leak" in the coolant, and you'll be okay with just the head gasket change. Have the head
check to make sure it's not warped.

It's amazing what an engine will go through and take and still keep working!

And change the oil every 5000 miles...

 

Cylinder Misfires | Page 3 | PriusChat

 

That's good!
Rust penatrant helps. Probably the one that's under the cooler on the head???
A 10mm 1/4 inch swivel socket will work. Then an inverted torx, not sure of the size,
to get the stud out.
Not sure about the other two, maybe on the back side of the cooleras it goes down the back?
I think they are 12mm? They are tricky because of the tight fit. You just have to fight your
way around it, easily and break them free. Then use the torx to get the stud off.
The gasket will fall, so try to be ready to catch it. But it should be replaced anyway.