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

I would say, if it is a head gasket, just swap the motor out with a Gen 4. It's a newer, low milage engine that has the common problems that are associated with the Gen 3s fixed. It's also less time and labor extensive than a rebuild. That's what I will probably do if mine goes out. I've got 209k mi. on mine, but I don't have oil burning like you do. Maybe a half to a full quart every 5k mi. Sometimes not even that. My oil is also very clean when I change it every 5k mi. I use full synthetic. If you're not loosing coolant, it may not be a HG. Do a little more diagnosing to verify if it is a HG. You don't want to spend that money and then find out it was something simple.

 

Here's also a video from The Car Care Nut. He is a Toyota dealership master mechanic who now has his own shop. He talks about how to diagnose the HG on Priuses.

 

Cheap/easy confirmation would be a block test (liquid-filled tube that test vapors in cooling system for the presence of combustion gases). If it changes colors, you 100% have a bad head gasket or cracked head. If it doesn't change colors, you might still have a blown head gasket but probably not.

You can also do a leakdown test to see if pressure is escaping the cylinder (and if so, from where it is leaking). If you haven't lost any coolant in weeks and all of your combustion chambers have comparable carbon deposits on your scope, then maybe you've got a stuck valve or something else going on.

 

Cylinder 3 has been known to go. You can just wait and see if it blows a hole or otherwise seizes. If not you win. I would get a professional diagnosis with less than one days pay before I put $2,000 to $5,000 in it.

 

Leak down test.

 

Compression test is useless. A leakdown test is different and more complicated. Only definitive if the leak is large, usually not the case with a Prius. A borescope inspection with a high quality camera often observes steam cleaned cylinders and occasionally drops of coolant.

Check the video in post 22 above around 7:40 of his diagnosis. You will notice he detects the hg failure right away and then pressurizes the coolant for more verification. It takes some experience and a very good quality borescope with several views, not a cheap $20 Amazon special. Sometimes spending a few dollars at the dealer or another pro shop pays off.

The bubbles are coolant. Could you see the head gasket with your camera?

 

It can be done quite easily.

After removing the cylinder head, you'll need to drop the stiffening crankcase assembly (you may have to wrestle with this somewhat heavy part if you're working without a lift) from under the vehicle, which will expose the connecting rod cap bolts (see picture).
Remove these using a 10 mm 12-point socket and you'll be able to push the piston/connecting rod assembly up and out of the engine block.
Immerse the piston in boiling water and tap out the piston pin. Voila, the connecting rod is now free!

During reassembly, you will need a piston ring compressor (free rental from auto parts stores), and some Three Bond 1207B to form a gasket between the crankcase and the block.

 

You'll have to remove the engine to get all the rods out.

 

I'd say if you are looking to rebuild the motor, it's easier and better to swap a Gen 4 than go through the whole rebuilding process.

 

What is the current thinking on Preventative Maintenance Routines that will extend the life of a Gen3 Prius head gasket?

I'm aware of the recommended cleaning of the EGR cooler and all the passages back through the intake manifold.
Also keep the engine coolant fresh.
Is there anything else?

I'm getting my third Gen 3 Prius soon. Bailing out on an 82 mile range BEV. I need a longer round trip for a new job.
This 2010 Gen 3 has 122k miles and I want to experiment with routines that might extend the head gasket life.

I'm also aware of 'Piston Soak' to help with high oil consumption.
A friend with a couple high mileage Prii confirmed that a few day Piston Soak helped a lot with oil consumption.
The oil control rings and drain holes in their piston grooves get 'carboned up', is the theory.
I think I will shorten the spec'd 10k mi. oil change intervals to supposedly help with this issue.

 

2010 seemed to be the worst year for oil consumption. Here's why modern Toyotas can have oil consumption problems. The Car Care Nut who is a retired Toyota Master Technician tells all about it in this video.

 

You would have to take off the bottom end, so probably not, unless there is enough room underneath to work between the subframe.

 

Most people with a lift drop the subframe, engine and transaxle to swap an engine or to do a rebuild that includes rings.

 

The oil pan in two pieces and you have to seperate it from the transmission to remove it.
But you you can only do it after you remove the whole block. So, no, you can't. Gotta pull it.

 

I will differ from Dogman and say that it is indeed possible; please see #30 above for exactly how to do this. You won't need to pull the entire engine, but the crankcase will have to be dropped to access the connecting rods from underneath.

You can follow this method without any of the following:

• separating the oil pan from the crankcase
• removing the entire engine block
• decoupling the transmission
• lifts
• an engine hoist
  
• a long-reach floor jack (I was able to get away with the Daytona 3-ton Professional from HF)

This is not the Service Manual recommended method for getting to the rings, but that does not mean it cannot be done. If you were to go strictly by the book, you would need to pull the entire engine just to get to the head gasket—we all know that is unnecessary.

 

Aside from regular coolant changes (~5 years), EGR cleanings (~50,000 miles), and oil changes (~5,000), I'd also be sure to use only top tier gas ( https://newsroom.aaa.com/2016/07/aaa-not-gasoline-created-equal/ ). It doesn't have to be the most expensive gas station - Valero, Arco, & Costco sell top tier and are usually about as cheap as any station...

I also wonder if higher octane gas would help prevent head gaskets from failing since we don't hear much about head gaskets failing in Japan, Europe, and Australia (but we also don't hear a whole lot from them anyway).