Car knocking, changed spark plugs, problem persists

oops

 

Most people think: we progress. Maybe not always?

I do think you're on to something: with every "gen" they've managed to eff something up, and the third gen was a biggie.

 

I am in Orlando and had no idea that the cars are much cheaper here

I bought a used high mileage 2010 Prius III 2 years ago. And after 20k miles, it didn't give me any real issue. This is (so far) of course. And I don't know what the future will bring. And I didn't know any of these serious problems Gen3 has before I bought it. But I don't think it would have changed my mind. There is no other car on the market at this price level that can get your 50+ mpg.

I experienced this infamous knocking issue about a week or two after I purchased the car. I checked the reason and when I found about the possible head gasket issue, I was alarmed. But then it never happened. I followed the "Do not shut off the car by pressing the power button if it is running" rule all the time. I did some basic maintenance like cleaning intake and the complete EGR system, replaced spark plugs, installed Oil Catch Can.

I experienced the knocking issue once again during the first start after the car sat in the garage for about 4 months and that was it. So far so good. (Knock on wood).

If I was in OP's shoes, I would replace the head gasket (not in the dealer of course. Not sure if they even do that). It is definitely the most logical option. Putting a used engine is really unnecessary. Who guarantees how long it will last? Trading the car is like giving it away.

If that engine didn't hydrolock and damaged the piston rods, parts will be a few hundred and a mobile mechanic can replace the head gasket on your driveway in several hours I would assume. All will be way under $1000. And the car will be back on road like new...
Of course you should consider doing it yourself if you think you can. I know I would try it my own

Think again...

 

I

I didn't know the "don't shut the engine off if it's running" was a thing bit I've always felt more comfortable letting it finish doing its thing. Good to know.