2011 Prius Head Gasket Failure

Brief background of the issue:

- On the afternoon of 2/24, I observed a loud knock at startup (lasted 3-5 sec) after shopping at Costco. Also noticed stumbling for several seconds after the knock subsided. On this same evening I started the car and it did not knock.

- On the morning of 2/25, the knock reoccured with the same intensity as previously. Check Engine Light comes on. The car was scanned and I found a current P0302 (cyl 2 misfire), as well as various pending and historical fault codes for P0302, P0300 and P0304.

- On the afternoon of 2/25, the knock reoccured (when I started the car to go home from work) and I decided to just park it until I had time to fix the issue.

- From beginning to end, I only had 4 start-ups (but 3 instances of knock) and drove a total of 42 miles. The coolant level also dropped about 1” during this time period.

- After the car was parked for 2 days, I removed the spark plug for cyl #2 and performed an inspection using an inspection camera. The top of the piston was wet with liquid (presumably). For comparison, I also inspected cyl #3 and it was dry. At this point, I decided to proceed with disassembling the engine for headgasket repair.


Relevant vehicle background:

- Original Owner, never overheated. Current mileage is 184,997.

- Oil Changes were done every 10k with 0w20 from 0-90k, then every 5k with 0w20 from 90k- present.

- No oil consumption between 5k oil changes

- Engine Coolant was replaced at 30k, 90k, 120k and 179k

- Spark Plugs were replaced at 92k and at 179k.

- Thermostat was replaced once at 122k.

- Engine Water Pump was replaced for preventative maint (no known issues) at 179k.

- EGR valve and pipe were cleaned around 160K (unsure of exact mileage, but around that time period).

- EGR valve, pipe and cooler were cleaned at 179K. The old cooler was moderately loaded but was not blocked.

I have ordered an engine overhaul gasket kit, thermostat, FIPG black and 10 new head bolts from Toyota. The Spark Plugs will also be replaced.

So far, I have 3-4 hours into it and have the timing cover removed. Still need to remove the chain, cam housing and then the head.

My plan is to have the cylinder head inspected, resurfaced and new valve stem seals installed. At this point, I am unsure of whether to have a valve job performed, so any feedback on this matter is welcomed.

This is just another data point for everyone. I requested and received a quote for headgasket replacement from a well-known hybrid specialist in San Francisco; they quoted $4800 + tax for the headgasket replacement (includes cylinder head machining) or $7500 + tax if I elect to install a new short block, headgasket and have the cylinder head machined. They strongly recommended the short block option if I planned to keep the car. In other words, if you have to pay someone to fix this issue, the cost of the repair pretty much exceeds the value of the car. Between the headgasket issue and the inevitable hybrid battery failure (anytime after 150K), these cars are essentially disposable once they are past 150K. Buyer beware.

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Where can you find a low mileage engine installed for $2500? I can't even find a low mileage engine for under $2k. But I guess it depends on what you define as low mileage; I would be looking for one with no more than 60k miles, and those typically go for around $2k:

2014 Toyota Prius 1.8L Engine Motor 4cyl OEM 63K Miles (LKQ~207060429) | eBay

Plus it is a lot more labor to remove and replace an engine.

 

Yep.

 

In general, the 2010s and 2011s are older than the 2012-2015's. That is my guess.

Why would I? There were no issues, and not a single occurrence of knock until the headgasket failure occurred.

I will check the block for flatness, but the cylinder head will be checked by the machine shop and resurfaced. They will also be installing new valve stem seals and checking the intake and exhaust valves for proper sealing. I prefer to have a second set of eyes on a critical component like that one. I just dropped off the cylinder head this morning and it should be ready on Monday.

The cost of new head bolts is very low and is cheap insurance considering the amount of time that this job takes.

 

It is a MLS gasket, and the failure is generally in the same area - between cyl 1 and 2. So, I am not sure if any of these items have any impact on the lifespan of the headgasket.

 

Update:

The cylinder head has been removed and was dropped off at the machine shop this morning for inspection, cleaning and new valve stem seals (supplied by me from the Toyota engine overhaul gasket kit).

It appears that the cylinder head gasket failed in the area between cylinders 1 and 2. As you can see from the photo, cylinder 2 was washed out.

Also, the bolt which came out of the hole that my finger is pointing to was looser than the other ones. Not by much, but it is coincidentally where the gasket failed.

 

The machine shop just called. They looked over the cylinder head and found no issues with it. So they went ahead and cleaned it in their solvent tank, resurfaced and installed the new valve stem seals I provided. Their total bill was $160.

After some thought, I decided to also replace the intake cam gear. Mine does rattle occasionally and it is a common issue with the 2ZR-FE engines in the Corolla (our engines use the exact same part). So, this added another $260 to my parts bill.

I hope to start reassembly on Monday.

 

The machine shop advised that the head was not warped at all. So, the resurfacing was done for clean-up purposes only and for restoring the surface finish to 20rA.

In other words, it was probably not necessary. But the side effect is that I may have higher compression now.