Head gasket timeline...

This is a known problem with first couple years of Gen3 Prius... The exhaust gas recirculation (EGR) valve was poorly designed and gets dirty and clogged, which causes the head gasket to fail. Regular cleaning of the EGR valve and adding a $10 oil catch can will prevent this problem. And congrats on extended warranty or gap insurance covering the cost. If they try to weasel their way out of saying it doesn't qualify for extended warranty coverage, make sure to come down on them hard with fact this is a known problem and they failed to properly service the EGR valve before they sold you the car, which means their negligence is directly responsible for the engine failure.

Also if you every need advice or work done, I'm near you in Olympia and am a Prius enthusiast and enjoy fixing them for a lower price than anyone else, which to me is a price higher than I usually make gardening & pruning. It's been a great supplement to my cash flow in the rainy months in recent years. But I primarily focus on battery reconditioning and repairing hybrids systems, but sometimes do other stuff mechanical too.

 

If the words "head gasket failure" ain't printed on the paper, it won't be covered. I'd be searching now if I were you.

 

There's been numerous replies here of people not connecting + to + or - to - and resulted in smokes and beeps. There's one in my signature.

 

It's not hard to change the Prius battery. 2 cables, Positive and Negative.
And a hold down bolt/nut, lift it up and out, then install the new one and
connect everything.
I'm sure there are youtube videos of how to do it.

 

I prefer putting these 12volts in as they're 1/3 the price and last almost twice as long: 12 Volt (12V) 55 Amp (55Ah) VRLA AGM Sealed Lead Acid Battery 55 AMPS HIGH CAP | eBay

The terminals are slightly different so you'll need some longer bolts than what came with it and some big metal washers to sandwich your existing terminals to it. I actually have one of these arriving on Monday and will probably order another soon after.

Also there's no core charge with this battery purchase, so you can take your old battery to a place like Advanced Auto Parts and they'll give you $12 store credit for your core, further reducing total cost.

 

I doubt 2012 onwards are immune.

 

As I heared it’s problem for new engines with direct injection in general - some are mire affected, some are less.

 

Direct injection engines get carbon encrusted intake valves. This can cause problems for sure.

But 3rd gen Prius, introduced an EGR system that:

1. Must be flowing properly, to keep combustion chamber temperatures from getting too high.

2. Is prone to clog.

 

It still bears repeating that, to the best of my knowledge, evidence has never been presented or cited in this forum for the magnitude of temperature difference from EGR flow restriction, the magnitude of "too high" needed to damage a head gasket, whether those two numbers are anywhere near each other, and therefore even if there is a correlation between EGR clogging and HG damage (which also seems claimed much more firmly than demonstrated), whether "temperature too high" is the mechanism.

There can be other effects of wrong EGR flow that might also be candidates for the mechanism behind the correlation ... if there is a correlation.

One that might be worth investigating (if anyone were inclined) might be fouling of the intake manifold EGR passages, leading to differences in the charge reaching each cylinder. The car has a MAP sensor that it uses to keep tabs on EGR flow overall, but there is only one for the manifold as a whole. Differences in per-cylinder flow are downstream of it and therefore invisible to the computer.