List of Maintenance/Service Items for a 2017 Prius 2 w/100k on the Odometer that blew a head gasket?

Without DTC's (Diagnotic Trouble Codes) it's hard to give advice. If the dealer has the car you might want to ask them what codes they got. Of course as you found out what's in a cars records doesn't always show the cars condition or what work was actually done to it.
There have not been any teports here about a gen 4 head gasket issue that's I've seen.
Again, the DTC's are the best way to determine what's actually happening with the car.

 

Thats pretty odd it blew a head gasket so early in its life unless it ran out of coolant or somehow got overheated.

 

Yes, near zero head gasket issues on 4th gen. The vehicle had some serious neglect?

 

It happens. Wonder why dealer sold the trade-in instead of selling it on their own lot?

That would have been a "red flag" that something was wrong.

I check if there is any head gasket sealant in the cooling system.

 

I wonder if all the chassis shields are in place? One thing this points out is you can't safely drive two minutes after a overheat warning comes up. Even on a gen4. Or else the head warps and the head gasket blows.

I have seen a Prius head bolt loosen up resulting in a warped head and gasket failure. One of the biggest specialty head gasket shops in California posted a video blaming gen3 head gaskets on thermal cycling which can be excessive on those cars.

Gen4 engines have significantly revised cylinder thermal management.

 

I think your case was a fluke that is unlikely to be repeated, certainly not on your car. Most likely alternate scenario is a water pump but the cylinder head temperatures may remain stable for longer since the coolant is still there.

I use a $30 monitor that has adjustable alarm points for normal data like coolant temperature and mph:

 

Ebay search p10 obd2 smart digital

It connects to the obd2 connector and uses the CAN bus to monitor ecu data. You can see the black cable to the left. I added an obd2 16 pin switch cable ($8) as well although their auto powerdown settings are fine since I drive the car every day or two.

In reality I would not bother on a lower mile gen4. I have 250k miles on a gen3 with lesser engineering.

 

Wow, I'm like others and surprised to see a Gen 4 with a blown head gasket. But, lesson learned, is to always have a good mechanic take a took over any used car we are buying (with the possible exception of if you know the owner good and they can show you maintenance records.) Those 1.8L 4-cylinders can easily get over 200,000 IF they are taken care of and fixing any little issues before they become big issues. The only "issue" with my wife's 2017 Prius 2 was when she accidentally backed up from the garage too far to the left and messed up her mirror hitting it on the garage door slide. (I didn't have to replace the entire thing, just a couple of parts on the outside cover..SO glad Toyota sells them pre-painted so you can't even tell it was broke.)
Hopefully you can get her fixed up and then take care of her for many years.

 

Interesting. It's the same Head - Block, no?
Do you have a reference for this statement?
"Cylinder Thermal Management" ??? What's that? Coolant temp?

 

Revised head, block, piston and cylinder thermal spacer among other cooling system changes.

 

Thanks for the detailed info!

Unfortunately more improvements are needed.
I say this because a friend with a '17 Gen4 just had the Head Gasket go bad at 205k miles.
He has had all the scheduled maintenance performed by the dealer he bought it from. $4800 repair for the head gasket.

Hopefully this is not a chronic failure point on Gen5's. Is it a dedicated new design engine for the Gen5, or shared with non-hybrids?

 

Early Gen 4 years were prone to coolant leaks in the exhaust heat recovery system. This lead to either misdiagnosed head gasket failure, or head gasket failure due to overheating, due to lack of sufficient coolant.

 

Maybe so. Does the Gen4 have a low coolant sensor in the reservoir ?

Anyways, that is not the case with this friend's Gen4. He uses it daily. Always maintained at the dealer. Sudden 'Shaking from the engine'.
Drove it to the dealer that gave him the $4800 price to fix the head gasket.