2010 Toyota Prius with bad head gasket
Peter Neilson's picture

3 Signs You Have A Bad Head Gasket In Your 2010-2012 Toyota Prius

Does your Prius seem different lately? Maybe you have heard a noise or your check engine light is on. If you think you may have a blown head gasket here is how you can tell.
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If your 3rd Generation Toyota Prius has been acting strange lately, you are probably not alone. As great as the Prius is, Toyota missed the mark on the 3rd generation initially.

Gen 3 Prius, as many owners have come to find out, is susceptible to head gasket failure. But what if you are not sure if your head gasket is blown because you are "not a car person." Well, that is why you have me, the hybrid guy who can help you navigate to see if you do or not.

To find out of your Toyota Prius has a blown head gasket check these three following items.

What Happened To The Engine Coolant?
Have you been told that your engine coolant is low when getting your Prius serviced? If so, you may have a blown head gasket.

One of the signs of a blown head gasket is that your engine coolant will magically somehow disappear. It has to be going somewhere because the cooling system is sealed and should never leak.

2010 Toyota Prius empty expansion tank

The 2010-2012 Toyota Prius, this can mean you have a head gasket failure. When the head gasket "blows," so to speak, the leak can go one of two ways. The engine coolant can leak into the combustion chamber and get slowly consumed as the engine runs and keeps the cooling system pressurized.

Losing coolant on your 3rd gen almost spells certain doom. To be sure, check the other two things below before you condemn it.

Does Your Oil Look Like A Milkshake?
Pull your dipstick or drain your oil. The picture I have here is after I pumped my 2010 Prius oil pan. You can see that the oil and coolant are mixed thoroughly.

2010 Toyota Prius Oil and Coolant Mixed

This contamination is a surefire way to tell if you have a head gasket failure. If you have this in your Prius, you need to get the vehicle repaired, which can result in a new engine if things are bad enough.

Does Your Engine Sound Like It Is Ripping Itself Apart On Startup?
Knock knock. Who is there? Cylinder number 1. That is probably one of my more favorite mechanic jokes, but in all seriousness, you need to pay attention to your engine.

2010 Toyota Prius Check Engine Light

If your engine sounds like it has a "rod knock" when it starts up, chances are you have been leaking coolant right into that combustion chamber. Your Prius is trying to get rid of it, which is why it sounds like the engine is tearing itself apart, that is because it is.

The bad thing about this is that while the head gasket is the issue, there can now be an even deeper issue. You may need to replace the engine as a unit. The reason for that is because after so long of trying to compress a liquid (which liquids do not compress) many times, the connecting rod bends and renders the engine useless.

Conclusion
I hate to say it, but if you have one or more of all these symptoms, you are looking at a hefty repair. You can try and do it yourself, but unless you have a few good years of wrenching under your belt, I would suggest you leave it to the professionals.

I also happen to have picked up a 2010 Prius with a bad head gasket, lucky for me (or unlucky?) I have all three of these symptoms. I will be doing more stories on this car as events unfold, and I can gather more data.

Thank you all for reading, stay safe out there. I look forward to seeing you in the next story. 3 Things 3rd Generation Toyota Prius Owners Dislike About Their Cars.

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Peter Neilson is an automotive consultant specializing in electric cars and hybrid battery technologies. He holds a Bachelor of Science in Automotive Service Technology from Weber State University. Peter is also an Instructor of Automotive Technology at Columbia Basin College. Peter can be reached on Linkedin and you can tweet him at The_hybrid_guy on Twitter. Find his page on Facebook at Certified Auto Consulting. Read more of Peter's stories at Toyota news coverage on Torque News. Search Toyota Prius Torque News for more in depth Prius coverage from our reporters.


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