What is the chief cause of head gasket failure on the gen 3

A friend of mine put his old boat gas in his prius and other vehicle one time. He couldn't figure out what was wrong. I was like well Wth did you do? He was like oh well i was told to just see if the old boat gas was still flammable and if it was to just put it in a vehicle to dispose of it. I said well how long ago was the boat ran? He was like hmm im not sure over a year or two ago. I was like damn man that a terrible idea. So to test our theory since the prius was knocking harder than your step dad we just put some more that gas in the truck. The truck eventually just slowly died like it needed a fuel pump. I was like yep... Sounds like you did it didn't ya. lol
We ended up looking at both gas tanks. Both had water and old gas seperated around in the bottom surrounding the fuel pumps. So both vehicles pumped basically hardly burnable fuel and water into the motors.
The low compression truck just quit running. No noise or anything. The prius actually knocked. So these 13:1 motors are EXTREMELY unforgiving.

 

That would make sense since the engine temps are hotter when driving on power mode and cools off when the engine shuts down.

 

Just found this thread! Looking forward to perusing all the theories and guesses.

But I can definitely say that pressing that silly little switch has no effect at all, except for remapping the pedal response.
Full Go Pedal = Full Power, no matter where that silly switch is.
Your car goes as fast or as slow as you command it to. You are the captain of your ship.

 

^ post #116, Nov 11

Still curious.

 

Then I don’t know what’s the cause of my Headgasket to fail at 140k miles. I didn’t have my fuel controller or pedal controller yet when I had my headgasket fail. Any other possibilities you can think of on my 15 Prius?

 

None at all.
That's the topic of this thread, but it's all speculation.

Could it be just a pisspoor design of the 'headgasket system' (block, head, gasket, head bolts?) on this particular engine?
Does toyota have any other engines that routinely have the head gasket go bad?

I'm just bidding my time with my '10 w/ 125k miles.

 

I’m thinking all headgasket son this generation isn’t design to last long. This is what my headgasket looks like after the failure. I replaced it with Felpro instead because you can feel more of the ridges by hand on the separation of coolant on the block.

 

As a matter of caution, I would change the ICE coolant at 50k miles and make the first change at 5 years. 10 years and 100k miles appears to be two long and in that time, the SLLC may degrade and eat away at the rubber compound in the head gasket; the most often point of failure as the coolant leaks through the breach in the gasket at cylinder number 2.

To me, it is cheap insurance. And, with the UView or other vacuum filler, the operation takes no more than 30 minutes as opposed to the tedious procedure specified by Toyota.

 

knocking is a good theory. Keep your egr system clean and especially the passageways to cylinder 1 and 2 and keep your testing going boys. At a certain point you just got accept failure will happen eventually or go buy something safer and newer and more reliable like everyone else so you don't have to worry. lol

 

i guess it's not the pistons and rings then