Is Head Gasket failure common in Gen 3?

you have to learn about prius engine more. there is no exhaust VVT in prius (intake only), and the effective compression rate is fixed.
mazda's skyactive has the variable compression rate, probably coming to toyota soon.

 

Just tossing your trash back over the wall.

Pixel XL ?

 

But that would mean the knock detection system is not doing it's job. How is that explained?
I agree, knocking under heavy loads can damage a head gasket and shorten the engine life in many other ways.
Does the corolla engine use EGR in any way?

I thought the Prius VVT system can allow the intake valve to remain open during part of the combustion stroke, thus lowering effective compression ratio. It's a pseudo-Atkinson cycle engine.
I thought that was how the actual Prius compression ratio is rated as high as it is. It never actually operates that way with regular gas, except maybe at high altitudes.

I wonder if any owner that cleans out the sewer pipe regularly still got the dreaded head gasket failure?

 

there is no cooled EGR in corolla, just some EGR due to valve overlapping during the exhaust stroke.

no, intake valves stay partially open during the compression stroke to allow for the Atkinson cycle.

this is a good question we don't have answer for, as not that many people cleaned the entire EGR.

 

If there's no VVT on the exhaust side that means there's a fixed expansion ratio. If the VVT on the intake does NOT change the effective compression ratio then what DOES VVT do?

Pixel XL ?

 

VVT-i - Wikipedia

 

Atkinson meets otto why the prius is so efficient

This was on Toyota's website last year. I think it proves that the compression ratio is variable and can increase closer to Otto-cycle ratios.

 

Interesting discussion for someone who bought used Prius III only a couple of months ago and wonders if it can happen to him. Could it be that clogging of the EGR happens mostly in colder months when engine stays below its optimal temperatures? I have an idea that taking care of that with grill blocking could save me the trouble.

Watching and logging temperatures of engine coolant on cold days I came to conclusion that Prius III has very serious problem with maintaining right (above 80 Celsius - sorry for the unit) temperature - especially when descending hills or even longer braking when ICE stops. After blocking lower grill temperatures went up 15-20 degrees on average.

Anybody here having troubles with EGR despite doing mostly long trips in a warm climate? And I don't mean guys who do cleaning because they think they should but those who had real trouble.

 

We know that the EGR accumulates sludge at an unknown rate based on engine load changes, engine temperature changes, the condition of the engine, etc. The "clean out your EGR circuit at 100k miles" advice is just a good round number that we came up with for people that want their engine to last past 200k miles and the 100k interval is not accurate in some cases. Nobody knows if its accurate. I cleaned mine out at 70k and it was over 50% restricted. I would expect taxis to need fewer cleanings. If you want more engine life then do more proactive maintenance.

As the deposits in the EGR grow steadily the owner will see a gradual drop in fuel economy, power. The peak combustion temperatures and pressures will slowly climb. It will insidiously increase head gasket risk over time.

To get precise numbers better than the anecdotes would require a coordination of lots of time ($$$$), experience ($$$$), and a large fleet of Gen 3 Prii.

A boat load of anecdotal stories could get us close to precision.

There are other maintenance items that are not on the Toyota maintenance schedule that can also cause the demise of the engine. Things like the engine coolant pump, PCV condensation in the intake, fuel system, oil leak, etc. Cleaning the EGR system is not a panacea.

 

@mjoo, thank you for your answer.

Anecdotal evidence is the only available source of knowledge for us most of the time. Toyota has wide knowledge base collected from dealers all around the world but its not willing to share it for many reasons. That's why it's good to have priuschat.

When it comes to knowledge base actually we have a tools to build it independently here. If everyone of us would go through some brief maintenance poll in our profile page - we would soon build our own usage/fail statistics. Simple data linking mileage with particular failure would soon build valuable source of predictive failure rates. I'm sure it would be fairy simple to code it into the site.

Did anybody here consider building our own statistics?

 

by Jon F. Thompson, Editor, Open Road dated 2008.
Is this guy with Toyota?
This is news to me. We need to research that more.
I heard only recently about Toyota moving to flexible Otto/Atkinson engines in their non-hybrid cars. I was almost positive Toyota's hybrid cars were full time Atkinson engines.

 

I followed your advice and googled. Found a few nice papers based on diesel EGR coolers. Conclusions were that after about 20% loss of cooling efficiency, the deposits stopped growing due to various factors removing deposits. I'm thinking when Toyota tested their cars they kept driving non stop and hence limited deposits. In field use in low temps, short trips, etc, maybe the deposits are not cleaned as much as they should with constant use?

I agree that the post cat EGR fixes the problem, it was mentioned in those papers too.

 

They never were true Atkinsons. Lower compression ratio in Prius is achieved by valves closing later in that cycle.

 

There's been a few pictures posted here, EGR cleanout around 200K miles IIRC, both the EGR pipe and intake manifold EGR "capillaries" (small diameter passages at each intake port) are near-completely blocked. The capillaries are barely discernible.

 

yes, I was talking about the published literature on diesel EGR coolers.

 

good literature review on ICE technology for fuel efficiency: https://www.theicct.org/sites/default/files/publications/PV_Tech_Trend_Engine_20180917.pdf

under Atkinson cycle:
To retain vehicle performance-older Atkinson-cycle engines [ie 2ZR-FXE and older] generally increase displacement or are paired with a full-hybrid system, where the electric motor returns the power to an equivalent level of performance by adding additional torque. However, the performance limitations are being over come by newer designs that include cooled EGR and wider VVT operating
ranges, such as the base engine in the 2018 Camry which increased power by 8% over the same size engine in the previous Camry (German, 2018). Hybrid systems of joint ventures, such as those of Toyota and Ford, use the Atkinson cycle to achieve improved efficiency. Toyota’s 1.8L 8ZR-FXE engine, used on GAC-Toyota’s Levin HEV and FAW-Toyota’s Corolla Hybrid in MY2018, is equipped with Toyota’s VVT-i to allow flexible intake valve closing time, with a geometric compression ratio of 13.0:1
[...]
Atkinson-cycle engines on non-hybrid vehicles are usually combined with high compression ratios. One example is Mazda’s SKYACTIV-G naturally aspirated engine, which was introduced to China in 2012. In the SKYACTIV-G engine, the switch between Atkinson cycle and conventional Otto cycle is enabled by Mazda’s Dual S-VT, a VVT technique. The conventional Otto cycle was used at high engine load for performance and the Atkinson cycle was used at part load for efficiency.

It's clear that Toyota is doing a catch up and introducing the mixed Atkinson-Otto cycle in new models in 2018. One way to tell if engine is full time Atkinson is max power. Prius' 1.8L 2ZR-FXE is 98HP vs corolla's 1.8L 2ZR-FE is 132HP. If Prius engine had the Otto capabilities, it's would have higher max power. It's not easy to do Otto cycle with 13:1 compression with regular gas. This is why it was such a breakthrough with Mazda's SKYACTIV.

 

And what is the ratio of PC users (and daily users) vs. Prius owners that have never heard of, or considered, using a Prius forum?
They just drive, change the oil, and hopefully comply with the recommended servicing intervals,,,
and then take the car in if, and when, a light comes on.

Some here think a squeaky clean EGR system is vital. Who knows? Toyota may know....
And that is why there have been incremental improvements in head gasket and piston rings on the Gen 3.
And a major redesign on the Gen 4 in terms of this nasty EGR system.

Only time will tell.
And only a few of the owners are the brave and thrifty that keep a car deep into the +200k mile range.

 

Challenge accepted.

192 k miles and going strong.

 

Challenge accepted.

182 k miles and going strong.

And NO SEWER PIPE CLEANING,,, afaik....

I bought this fantastic car a few months ago and I have the detailed service history from Toyota,
but I have no way of knowing how much, if any servicing was performed at any independent shops.
(there are a few oil changes missing.... but multiple ATF changes, filter changes and one spark plug change. What a great owner !!)

Plus I'll contact my Bud in the Bank Courier business and get more detailed info on his Prius and others he knows. (I'm pretty sure they don't dik with EGR cleaning....)
He'll probably say "182k miles? Hah, it's just getting broke in!!"

 

Whistling past the graveyard?