Bought a 2012 For $700

Okay then...
Well that is good for you! And you got a great deal!
But your labor is not free. How much is YOUR time worth?
It's just an expense you did not have to spend.
Overall, you have a car that will last you a long time, and hopefully, trouble free.

By the way, did you clean the egr circuit?

 

Well, If you say $100 an hour for labor, that is at the least $1600 you didn't spend!
You could get another Prius with a bad head gasket! Hopefully, with a good wind shield!

 

Is the coolant level stable? If you are not losing coolant, the smoke would not be antifreeze.

 

How long did the cloud last? A few seconds, several minutes? At your parts store, do they have a coolant pressure test kit? If so, borrow it and pressurize the cooling system. If the pressure is steady, the cooling system is intact.

After I put my engine back together, I drew a line in Sharpie on the coolant tank to indicate the level. I measured it every drive with a machinist scale. If temps and level are steady then it’s not coolant.

I know this doesn't answer what it was, but it will show what it’s not.

 

+1 on what cnc97 said. Knowing what its not helps determine what it is. Eliminating coolant as a factor would be a major clue.

Also, like cnc97 says, how long did it last?

Finally, are we talking thick white smoke or vapor like white smoke?

With any luck (and you could use some luck!) its just condensation build-up within the exhaust system, which would be consistent with a slort lived event (burned out fairly quickly) and vapor like white smoke. Also, it is pretty cold in Oregon, which is prime condition for condensation build up.

And it might be beer!

 

When you put the head gasket on the motor you bought, did you pull the PCV plate off the side of the block and clean it out? If the engine only aspirated the junk caught in there, that would explain the short duration, and inability to recreate the episode. It also explains why your coolant and oil in the car now are clean and steady on level.

 

This was my number one piston at 213k miles in July of 2018.

 

Not seeing a gasket listed on the Toyo parts website, so FIPG (sillycone)(deliberate misspelling)is a safe bet.

 

Yes, it's form-in-place type gasket. I believe Permatex Ultra Black* might sub for the spec. in attachement. Or Permatex Right Stuff? I think the latter cures quite fast though, pros and cons to that. For a small panel mostly pros?

The technique the Gasket Master guys use for applying the fipg has been met with some derision here, but I 'm not so sure it's bad. The Repair Manual says to apply a continuous 3 mm diameter bead. Well good luck with that?

The GM guy just goes along putting dabs, every 1/2" or so. Then he goes over it with a finger, and if he detects any thin spots, adds a little more.

This I suspect is easier to do in practice, easier to get the right amount, uniformly, and ultimately just as effective.

Maybe the main issue is: it's hard to describe such application technique, in the Repair Manual??

* Permatex Ultra Black was recommended by Gasket Masters in their latest head gasket video, For use on the timing chain cover, fwiw.

 

Guess I'm going overboard: I've never done ANY of this, and you've had the timing cover off umpteen times.

 

The “stepped” thread on tip for the squeeze silicone starts with a .125” hole if you can get it to cut straight. That’s 3.175 mm bead. I think the “cheese whiz” can is a bit larger, .150. That’s a little over 4mm. But since it’s not 3mm, as the factory intended, it will never work right(heavy sarcasm intended). I’d rather have some excess, within reason, ooze out the side, then risk missing a spot.