I don’t have reliability data for Toyota’s head gaskets, but the part has changed several times since the launch of the third-generation Prius model. The original service part number was 11115-37051. This was superseded by 11115-37060 in December 2011; by 11115-37061 in October 2014; and by 11115-37062 in November 2021. The last is the current service part number, for the head gasket only (not the kits), for all third-generation Prius, Prius v, and Prius Plug-in (2010–2015) cars. I don’t know the reasons for these changes, which don’t imply that the earlier parts were defective. Parts can be changed for many other reasons, such as cost reduction, manufacturing efficiency, or commonization.
OK, getting progressively more childish. But I'm all for that! So, whatever, right backatcha! What does imply the part was definitely defective (or the head/block design) is the chronic failures of this part. What more evidence do we need? At this point even toyota does not have 'reliability data' on all the head gasket repairs out there in the world. This is a 13 year old engine at this point. There are Mobile Pit-Stop-Like Head Gasket repair services. Do you think toyota gathers data on outside-the-dealership repairs? I don't think that's possible. 5 strikes and you're out. I'm going with the FelPro, when my time comes. (Or Blue Devil and sell it quick,,, like I did with my second Gen3.) (And get an affordable used BEV,,, ya, right.. I'm selling an EV and bought this current Gen3, bc I need more range.) Even if I change engine coolant and clean the complete EGR circuit every 100k miles, what are my chances of this part of the engine lasting a long time? Is there data on this forum about that?
Oh, here's an idea! Start with the biggest font for the w and the smallest font for your last r! COOL The kids like this stuff!
I tried to find on this website what this set looks like and couldn't find it. Engine Cylinder Head Gasket Set - Toyota (04112-37254) There are also questions about some of the o-rings from this kit. It is not clear where they are placed. Strangely, this kit doesn't come with 2 o-rings for the oil filter housing. They could have packed it better. The the exhaust manifold gasket lies on the head gasket.
You're in luck, @NutzAboutBolts has just posted a head gasket video, starts off part 2 with a thorough explanation of the Toyota gasket kit parts: here: Nutz About Bolts Prius Maintenance Videos | Page 28 | PriusChat Also mentions several that were not included, which he purchased separately. I've always gone back to the kit part no in the attached, when the question comes up, not sure if it's still the latest.
The "?" on the right of the part number sticker, I believe one goes in the front of timing cover, and the other goes on the head under the cam shafts, or on the valve cover. You have to look closely, because it's small, easily missed. I forget where the left "?" ones goes, sorry. It's bee a year...