2010 Prius Blown Headgasket

Mileage 192k. Signs...stumbling/rough engine startup for first time of the day and anytime the engine sits for a few minutes before turning on again (battery charging/speed high enough for engine to start, etc).

2010 Prius engine start stumble - YouTube

Started out with no code, then check engine light started coming on. P0301, misfire cylinder #1. Sparkplugs were replaced, and coil pack for #1 switched with known good one. EGR tube also cleaned of carbon.

Stumbling/roughness has been getting worse, about an inch of coolant used per week of driving. No oil in the coolant, and no coolant in the oil (no milkshake or anything like that).

Dirty fuel injectors were suspected, but no improvement after using Techron. Finally, a boroscope was used to inspect the cylinders through the sparkplug holes, and a very slow leak was found in cylinder #1. Since liquid cannot be compressed, during the compression cycle significant misfiring occurs.

 

Going to replace just the gasket, the engine is fine at the moment. Once oil gets in the coolant and vise versa, then an engine replacement is better.

 

Dealer charges 4500ish. Hybrid shop, aboud 2700ish.

192k is early in my book, but then again Toyota's headgaskets especially on their sixes don't have a good history.

 

This is the engine cylinder head gasket, there is no white smoke at all. I know it's a little odd for this problem to be happening now. I am fairly certain that the intake manifold has no coolant in it.

Edit: I found a shop that will do it (ASE certified) for flat rate labor plus machine shop fee ($60) and I bring the parts. This particular shop warranties the work but only if you bring parts in a set (example headgasket set, not individual parts).

So far partswise I've ordered Fel-Pro HS26515PT (headgasket kit), and the bolts will come from Autozone since they're not included in the kit. Also supplying a gallon of coolant, oil and filter for change as part of the process.

 

No history of issues, there was a time when it was using extra oil, and I countered by adding seafoam to the crankcase and also to the gas tank, and the quart/2000 miles issue went away to a more normal quart/8000 miles. The only thing i could think of that could exacerbate would be I used B mode in the city (SF) more than probably most people do/would.

The coolant usage popped up in the last 5k miles or so, and check engine light (misfire, p0301) in the last 2.5k.

As a side note, the hybrid shop i took it to said they've seen more gen3 headgasket failures than on gen2.

 

I got the idea that it was probably on the order of 10 vs 5, tops 15 vs 7. I couldn't see them doing more than that. I also got the idea from them that the average Gen3 models just don't have enough miles accumulated to be a good reference for when these things might start to fail. From my calls with Toyota (three dealers and customer care number), none of them had heard of it happening yet. There's a blog that references the roughness on startup issue that the 2010-2011 models are known for having (stickied thread in this forum) as being linked to a headgasket issue to begin with, but I'd say my symptoms grew more and more severe over a month's worth of time than your average Gen3 Prius.

 

My advise to you would be to get a USB borescope from your favorite online retailer and check it out. Do you have coolant usage? If you have less than 60k miles you might want to try the Toyota 800GOTOYOTA number and document your problem, and perhaps have it checked out by a dealer. It has to be a Toyota dealer, and they claim they only accept service history from Toyota dealers, not anyone else. Which is funny, because in CA at least, it's law that you can take your car anywhere for service and still maintain the factory warranty.

EDIT: and assuming all the above requirements are met, then you could attempt to have them cover the repair under goodwill.

 

Same here, my MPG has dropped about 5-10MPG overall. Well, as long as you don't have coolant loss then all you can do is monitor it and wait I suppose.

For the borescope, here's an idea of what you'd see (and what I saw on Prius with the shop's borescope, though my leak was not as bad, much much slower, like a small drop/5 minutes or so).

EDIT: I guess I didn't really answer your question about the borescope: Basically it's a video inspection tool which allows you to see inside the cylinders through the sparkplug hole without tearing the engine apart.

 

Yeah I saw that thread....Jumped from 32 MPG to 56.6MPG - Heres How | PriusChat

I wish mine was so simple...but with coolant in there...definately not my issue. I'll probably take my manifold while it's in the shop to get the injectors cleaned while the whole thing is apart.

 

The borescope on your favorite online retailer is about $20-40 for a USB version.

About the sealer stuff, I don't believe in using that stuff in a car with an electric cooling system pump. Too many variables at stake here, and I want to take the car to another 200k miles, so I might as well as fix it the right way. I depend on the car every week and can't risk it failing early or because of an additive to the coolant, even though the risk is probably low. I might as well get it done the right way so i can trust the engine to last.