How to prevent the 3rd Gen Prius Headgaskets failure!

Yes... This are all theories...

I think no one here knows all the dependencies between all the factors.

Maybe even a Toyota engineer would get into trouble interpreting all this and getting some clues to prevent blowing the HG...

Mat

 

Detonation is premature explosion of the gas/air mix. With failing head gasket there’s “similar” knocking, but due to pistons trying (without success) to compress coolant that’s leaked into the combustion chamber.

 

But if the coolant is already leaking into the combustion chamber, it is too late... The gasket is already dead (even if the engine is not yet dead ). It can come even worse... After you stop the car and park it over night, the coolant is hot and under pressure - if the HG is failing, it can happen, that the coolant can enter a cylinder (no pressure here) to the extent, that there is more coolant in the cylinder, than the volume of the combustion chamber itself... The first attempt to start the engine can damage it seriously... This has some name, I do not remember.

In this thread we are actually looking for measures to prevent the HG from failing.

Cleaning of the EGR pipes and valve _can_ be one of this measures, even if there is no really scientific evidence to help, there is some suspicion it may help. And it is much easier to clean the EGR, as to replace the HG or even the whole engine...

Mat

 

Agree with everything you said: when the engine is knocking, to Gasket Masters you'll be talking. Or walking...

And, if intake manifold EGR passage at cylinder one is first to be completely carbon-bunged, and head gasket failure happens there?

 

The compromise that makes the best sense to me under the current state of knowledge is to occasionally remove the intake manifold physically to examine it and clean its EGR passages, and combine that with occasionally asking the car for its overall EGR flow monitor results, and using that information to guide whether and when to do the more invasive EGR cooler cleaning.

Rationale is that the monitoring system easily shows the overall flow adequacy, but it is blind to per-cylinder differences at the manifold, and the manifold is such a quick easy job that physically checking it is very little trouble, while the cooler is an exhausting job (sorry), and the suspected damage mechanism from uneven manifold clogging is the best supported so far.

 

The reason, I'm reading and writing here is, I'm trying to get a procedure to make my Prius to last

My Prius (2009, one of the first gen 3) is now at 95 000 km (somewhere about 60 000 miles?), short trips, never cleaned the EGR, intake manifold, never thought about PCV valve, on original spark plugs, so I have a few things to do, if it shall run another 100 000 km or better more

But it is actually something for another thread.

Mat

 

I'd clean the full EGR system by 100K miles, then every 50K miles thereafter. That's the same as the mileage element of the Toyota USA engine coolant replacement schedule, which makes it convenient, no spillage. It might be a good idea to shift the spark plug change (from 120K) to 100K as well, just to take advantage of the cowl being off.

What's your approx location btw, say what country?

 

I'm in Europe, Poland.

I think, I will make here a new thread, as soon as I get to some conclusions, of what is to be done now, what can be done later, in which order should it be done, if it should be done optimally.

Mat

 

An excellent way you can contribute to the state of knowledge on this issue is to post the EGR flow monitor result for your car, at the current 95,000 km or at any chosen point or points before you do the cleaning. Many smartphone apps, as well as Toyota Techstream, easily obtain the value; it is as simple as plugging in to the car's diagnostic port and asking.

Naturally, if collecting this value is overlooked before cleaning, it is then too late. Our thread for that data collection is this one.

 

I could of course!

I have even another Prius in the family, with similar mileage but from 2012 - would be interesting, if there are differences at nearly the same mileage.

Can I get the values without Techstream?
I have a OBDLink Mx+ - it could be able to read this values.

Mat

 

Any scan tool or phone app capable of grabbing standard OBD-II "mode 6" monitor test results.

You'll see some examples in the data collection thread linked above.

 

I have OBDLink MX and Car Scanner app.
I can see EGR flow in Noncontinuous Monitors section of app.


BTW, I'm still monitoring it since I cleaned IM and EGR pipe and usually I'm in 19's kPa with some dips in 18's now and then so I'm still thinking if I should bite the bullet and clean EGR cooler.

 

I'll try this with Torque or with OBDLink app, but not today - it is already dark here

Mat

 

So! Next day here and in the night I remembered, that I recently did and saved a test on my Prius.
What turned out - the mode 6 tests are there

My result:
Value: 19,94 kPa (tested on 15.05.2022)
Min: 0,97 kPa (I see the min value slightly different in other peoples results - has it any relevance?)
Max: 655,35 kPa

The car:
94 697 km (58 842 miles?) at 19.05.2022
Production year: 2009 (Europe, sold in France, imported to Poland with approximately 55 000 km)
Very short trips in average.
The average from the last 500 trips, almost 2 years of driving is about 9,5 km (I'm surprised myself, but I realised, that trips of about 200m from my flat to and from my garage are inside ).
Average consumption over this 500 trips: 4,4 l/100km (53,46 MPG) - not bad for this old car

I will post this data in the other thread, that ChapmanF pointed out.

Have I missed something? Let me know.

For the second Prius in the family, I have to do this test first. Then I post the data as well.

Mat

PS. What would you think about the 19,94 kPa result?
PPS. In the same set of data I encountered something like "Hybrid battery pack remaining life: 44,31%". Someone here knows, what this would mean?

 

Best value we see (after cleaning IM/EGR pipe/EGR cooler) was 22.xx kPa so 19.xx sounds good to me. I guess.

That remaining life is probably from Dr. Prius app tests. Not very encouraging on long term but for now it works.

 

That remaining life is not from Dr. Prius app tests.
This results are from the OBD Solutions (makes the OBDLink devices) own app, and is shown in a "PID Snapshot" section of the results (it states "39 PID values available", but shows 43 values), so I would think, it is some PID value or a value calculated from some PIDs, but of course not sure

Mat

 

Nice one. Didn't know that. I have their app but never used. Now you give me a reason to take a look on it.
Thanks.

 

Yeah, since my cleaning last year I've been seeing 21ish to 22 kPa (the monitor test is snuck in by the ECM during normal driving, so it doesn't have perfect control of the conditions and a little variation is normal between tests). So that seems to be about where a squeaky shiny clean system ends up.

What we don't really have enough data to conclude, yet, is how much lower than that you should be comfortable letting it get before cleaning. The test's "min" limit is way down around 1 kPa and you'll get a P0401 code then, but there's some concern around PriusChat that that's too long to wait. I cleaned mine last year when it was around 10ish.

So, until we know more about what numbers are low enough to cause problems (or, indeed, whether any numbers are low enough to cause problems), it is kind of a number you can watch to see how close to freshly-cleaned you are, and how quickly it seems to be declining over time, and apply your best personal judgment to decide when you feel like cleaning it.

 

Am I right, assuming, that if I clean the IM and the pipe connecting the cooler with the IM, I should not see any major change in the results of this test?
I think, the cooler is the main thing restricting the overall flow in the EGR system.
The ports in the IM are responsible for the evenness of flow between the cylinders, right?

Mat

 

The intake manifold egr passages are the only “exit” for those exhaust gasses, so I’d think their percentage of blockage would be in lockstep with flow reduction.

It’s somewhat akin to clearing leaves from a gutter on a rainy day.

Ah, I read that wrong, missed that the intake manifold was cleaned (somehow...). Anyway, yeah until the whole circuit is cleaned, the portion still clogged continues to obstruct the flow, and the cooler can be very clogged.