Cylinder Head Gasket Failed

Hello I am new to this forum. My car is a Prius 3 2012 150,000mi. My mechanic said the engine is full of carbon, and the cylinder head gasket has failed. Estimated cost of repair is $3,200. Car was worth $5000 at the beginning of the year, then I spent $2,000 repairing several things, and now it will cost $3,200 more to repair it. Should I fix the car or take it to the junk yard?

The Prius exhaust and intake system were removed and they are plugged up with carbon. They also found that the cylinder head gasket failed and it developed engine surging. They cleaned both the EGR exhaust and intake system but the cylinder head gasket needs to be replaced in order to correct all the problems.

A separate issue is that the engine also burns a lot of oil I replace the oil at the recommended time, and always it is barely enough oil in there to run. Multiple mechanics have said this. Other than these issues I can’t think of any more. I bought this from a dealship for $10k 100,000mi. Now it has 150,000mi, and needs at least $3,200 of repairs, likely more. Rest of car in good, but not perfect condition.

I am not a car mechanic, I don’t do any personal repairs on my car. I need to get to work.

Should I fix the car or take it to the junk yard?

Not enough info to even make a guess. So the big question is WHY the head gasket failed; assuming the diagnosis is correct.
So what is the mechanic’s reasoning for the failure?


A quick check shows that the 2012 is selling for $9,000 to $13,000

What does your mechanic say it would cost to fix yours ?

Can you replace it for what it would cost to fix it ?


As I and others have said , this is a lousy time to be vehicle shopping . The selection and prices are just unreal. If you can repair it for a resonable amount ( only you can decide that ) and wait for at least 6 months it might be better for selection and price.

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In today’s overpriced market, I’d do anything I could to avoid needing to purchase another vehicle. That would include fixing a car which technically isn’t worth the cost of repairs. In your case, the car is certainly worth the cost of repairs, and you won’t be able to buy another similar car for less than it costs to fix this one.

BTW, if the engine is indeed full of oil sludge, I would only attempt repairs as a DIY project. The probability of further problems is too high. If you have to pay someone else to do the work, have the engine replaced, either with a low-mileage used one from a junkyard or a remanufactured engine. And maintain it better going forward.


There are symptoms displayed when a head gasket fails.

Is the vehicle displaying any of these?


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Rule of thumb: Get two or three estimates to have your car repaired. Then think about shopping for a used car exactly like yours and ask yourself if you would buy it for that amount. The advantage of paying for your current car is that you know something about its history.


What are the symptoms?

I am suspicious of “full of carbon” and that makes me question this mechanic’s judgment. In any case, for a major repair like head gasket, it makes sense to be very sure before going in.

I didn’t say it was full of oil sludge, I said it was full of carbon.

Who are you talking to? Did you read what I said?

OK , that tells me that you have not been checking the oil level on a regular schedule . That is why it was always low at oil change time . That causes engine damage so it might be best to just let this thing go .


What do you mean by maintain it better? I did everything every mechanic said I must do. Please be specific if you say there was something I could have known to do that I should have done.

he bought the car well used, with 100K miles on the clock, so even with his statement that oil is regularly replaced (but not checked!!), it’s a good chance the prior owner never planned on keeping this car long and neglected it.

that might explain that carbon is all around, but to the @ok4450 question, it’s not something suggesting that headgasket is the culprit, it’s far mode likely that the entire cylinders/pistons/rings system is worn to the ground and engine may be shot… or it may be rings coked and it has some chances to be recovered (at least partially), it’s just not information to go, but the entire “replace the headgasket and you gonna be golden” premise is very suspicious

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I didn’t say the oil was at a dangerous low level, I only said it was at a low level. No mechanic ever said the oil was below a good level, only that it was lower than optimal.

Don’t try to B.S. me.

You edited your original post and it didn’t include what you added after the first paragraph.



I almost feel like several of you are just guessing what is going on. I told you what the owner of a professional auto repair shop reported to me, with pictures. I didn’t say the head gasket might be the issue, I said it is the issue. Start from there.

Another point. I read at least 2 of you are surprised I am not regularly checking the oil level personally? There is a light on the dashboard that will tell me if the oil is low, and in the several years I have owned this car, it has never come on. Do you know why it has never come on? I’ll tell you, because every oil change mechanic has told me the oil is not at a dangerous level. With 1 exception, I don’t know anyone in my family, friends, or professional contacts that personally checks their own oil level. Is that unusual for a normal person to not do that?

He sent me 4 pictures of the pipes with carbon.

Look at the main post.

Those engines have oil consumption problems and leaky head gaskets. There is a service bulletin with revised pistons for the oil consumption issue.

Thank you Nevada.