Considering Head gasket replacement - 2011 Prius - 215k miles - P0303 misfire

The EGR valve opens under certain rpm/load conditions. Some other factors likely in play. And some head gaskets maybe just hang in there longer than others. But I think it's fool's paradise to think you're gonna dodge carbon clogging, or significantly delay it, with some driving technique. Toyota screwed-the-pooch on this one.

 

Yeah, sure, it's probably gonna happen eventually if the car is driven long enough. But what, if not "some driving technique," explains the inconsistencies you can see in our ongoing EGR blockage test thread, Techstream EGR Valve Blockage Data | PriusChat ? Something is causing the rate of fouling to vary significantly.

 

How you drive absolutely matters in how long the engine will last (and how much carbon will build up). The prius engine is most efficient when putting out between about 12-33 KW (~15-45 horsepower) which is about the power output you'll get when driving in the top 3/4 of the "eco" range of the hybrid system indicator bar.





That's the power output needed to accelerate moderately and/or maintain about 60-80mph on flat ground (windows up, no roof rack, only driver in car, etc). Anytime the engine is running outside of those zones, it is doing so inefficiently.

Very slow acceleration is inefficient. Full throttle acceleration is inefficient. The engine idling to recharge the battery is inefficient. Inefficient operation will burn more fuel than necessary which means more deposits. The engine is especially inefficient when it is first warming up so if you combine the above operation with frequent short trips (lots of cold starts) you're far more likely to cause carbon build up.

You're also more likely to have extra crap breaking down the oil which is why a car that spends a lot of time idling on & off battery in gridlock should change its oil every 5,000 whereas a car spending all its time at highway speed can do 10,000 mile intervals.

 

Thanks for posting this!
Now I have a new rabbit hole to look at....
Haven't read through the 12 pages yet, but in summary,,,,

Do you think there is a correlation between EGR system 'cleanliness' and head gasket failures?
Like, once the flow is below an expected range, your head gasket will fail in X amount of miles?

Some have theorized that the #1 and 2 cylinders' egr passages in the intake get clogged first because of the distance traveled (and has time to cool and condense in the tracks?) and,,,

that creates spikes in Combustion Pressures in just those cylinders (which isn't detected as 'knock') and,,,

even if the engine seems to run smooth and quiet, those pressure spikes in those two cylinders concentrate 'somehow' to take out the head gasket at that one common area and ,,,,

If you keep the EGR system clean, it will allow the engine to run MUCH longer without a head gasket going bad.

And now your link shows a way to quantify the cleanliness of the EGR system? !! I hope that's the case!

edit: I had the dreaded 'knocking/rattling start up' once in my previous '10 when I was putzing around in very humid conditions the night before. This car had the original intake manifold (which I think is the older design).
My theory on that is: 'Carb Icying', ie. humidity is possibly building up as ice somewhere in the intake system.
Then it melts and pools up after shutdown.
So at start up the engine is digesting a small amount of water into some of the cylinders.
Now THAT is bad. Hearing the knocks is definitely hard on engine and maybe the head gasket.

Supposedly there is a newer style of intake manifold that addresses this problem.
Does anyone know how the intake manifold is physically different?
Is it recommended to buy and install this upgrade at EGR cleaning time?

 

This video is definitely worth a watch:

And this:

Also, there's a couple of head gasket related links in my signature, one for @The Critic's thread, and the other has some repair manual excerpts.

One thing with the first video (linked above): the driver they use for the head bolts is NOT ideal. It's a triple-square (has 90 degree corners), and Toyota calls for a double-hex (has 60 degree corners). Their triple square "works", but has corners at a slightly larger radius, and doesn't fit flush against the head bolt's socket interior faces. More mention here:

New head gasket replacement video from Gasket Masters | PriusChat

Full disclosure: I've NEVER done a head gasket replacement, or anything near as involved. Just trying to accumulate info.

 

Engine block coolant drain will only drain coolant from the coolant circuit, the places coolant is supposed to be. And it's not very effective at that.

Not sure I'm missing something, but if there's coolant "in a cylinder", paper towels??

Post a pic of the head gasket?

 

When you took the head off coolant would have spilled into the cylinders. Cleaning the cylinders with a rag is all that is necessary. If you have the head off it should look like this:



Perhaps you mean "how do I get the coolant out of the passages around the cylinder." Otherwise, if coolant is still flowing into the cylinder on top of the piston, you may have a cracked block.

 

You can suck all that mess up with a shop vac including out of the coolant passages Make sure you have the wet filter in the vac. More important than this now is to look at number one and two it's usually two that sets the code cylinder that is but whatever it can leak over to one and over to three two I guess at the passages were busted on the head gasket or became compromised. Now you need to be looking at especially number twos piston carefully. And I mean carefully. They tend to break the skirt off and then they try and roll over in the boar which breaks the rod up near the small end which is on the bottom of the piston gudgeon pin sometimes they're called wrist pin in America. I replaced my engine because of this head gasket leak. And that's what I would do again with a 2z engine

 

There's water in the passages that can get into the cylinders when you remove the head.
But a shop vac can suck 99% of it out. Brake cleaner can disapate it and clean up with a rag.

Does the top of the piston look cleaner than the others? Or do any look cleaner?

 

Yeah below the pistons it's completely open to the crankcase.

 

Looks not too too bad. But personally if I ever was to even consider attempting this again the oil pan would be coming off so I can see the rod whatever. And I know that the center girdle and all that the open deck engine and the way that it's made is a weak design so if I'm pushing anywhere near 200,000 miles which Toyotas are reliable for way more than that but apparently the ZZ engines are not even in Corollas they're burning oil like crap at about between100,000 130 or so almost similar to Prius w same engine.. so I would have to pull the pan and really look carefully by the time I pay all the money or my time doing just the head hell I've almost spent the money for a JDM spec engine just the engine itself I bought an engine in transmission so I would have an engine and transmission with similar mileage when I put it back in the car so I wasn't putting a 65,000 mi engine up to a 250,000 mi transmission basically was my issue. But that's just me personally after seeing what happened with one I wouldn't want to risk it again

 

I'm not sure if it is just the angle of the photo, but those cylinder walls look scored, burned.
Probably because of the clogged oil ring?

There are 2 oil "O" rings that go on the oil filter housing. The will fit into the grooves in the housing
there go against the holes in the block.

 

The oil filter "housing". It's what the contain the holds the oil filter screws into.
There are 2 large/thick "O" rings that fit on the housing. Then you bolt it to the block.