With the talk about blown head gasket in the Gen4 forum...

If the level gets too low, air bubbles will be flowing through the engine. This messes with the heat transfer from engine to coolant.

 

Standing back and looking, having a coolant loop is on every water cooled car. Two loops one goes inside the car to heat the cabin. People even add loops. So the coolant loop to the exhaust is so different? They had it for 12 years. Before that a coolant bottle loop on the gen 2. That a lot of writing loops. Somehow I am not expecting a problem with it like it’s being made out to be on a 2020.
They even have inverter coolant loops and long loops to rear heat-a/c, and to heat/cool ev batteries. The gen 5 has a refrigerant loop to the battery from the front according to car care nut. Does it have coolant going front to back also? So to cool the battery the a/c must run?

 

What if they have help getting rid of it?

In the heating season, when the engine is stopped, the pump keeps sending the coolant through the cabin heater. The heat you're getting is the heat the chunk of metal is donating. So it's being actively cooled down.

I don't mean that as insisting on the expansion/contraction story for head gasket problems; I don't really have an opinion on that one way or the other.

 

And leaks can happen in any of those loops. The possible one with the exhaust loop in regards to the topis is that if happens, it isn't one easily noticed. Instead of a puddle on the driveway, the coolant goes out with the exhaust. Making it easy to miss until too much coolant is lost.

Several EVs and hybrids have used AC refrigerant lines for cooling. I believe it works in conjunction with air cooling for most. So the compressor isn't running all the time for the battery.

 

I had looked at Miller cat shield pictures and for mine I see what looks like a heat exchanger fed by two hoses, and possibly some kind of thermostatic piston to regulate the flow of coolant, as a guess to what it is. So how does coolant get into the exhaust? I tried to show the picture but didn’t work.

 

i'm not sure anyone has ever posted details, but it's some kind of internal leak. bad weld or something?

i haven't watched it yet, but this might be informative:

watch

here's the guy that claims they are starting to replace a lot of gen 4 head gaskets.

watch

he mentions metal fatigue from heat being the culprit around 2:20

 

I looked up some thread here, and in 2019 they updated the coolant gizmo. I guess I am ok for a couple weeks on my 2020. So if we had an old fashioned temp gauge would that be worthwhile to have? I guess we have a warning light.
Watched video, pretty good view of it.

 

idk, someone said air gets in the system and the temp sensor doesn't work.

 

Just regularly check the coolant level.

 

Crud...I thought Toyota had supposedly "solved" the head gasket issue.

Currently looking into used Primes, as the prices seem to be coming down a bit. Having second thoughts now.

Ironically, the ONLY Prius in our fleet (present and past) that hasn't had some sort of engine issue is the Prius C that my daughter now has in North Carolina.

I may just keep shopping for another Prius C...but any sort of good deals on them are elusive.

 

i think if i bought a gen4, i would just do the coolant loop hack and not worry about it

 

You probably realize that you are going to confuse the PC “experts” with the facts, right.

 

Which helps it cool evenly and safely. Not dangerous at all.