My Son, who has my wife's old 2011 Prius came over. His Prius is showing an intermittent Check engine light. I pulled the codes and the first code was misfire (and the rest too). Then we opened the hood and looked at the coolant level. It was down 3 inches. After making several comments that I should not post here, I told him he had a head gasket problem. And this is despite all the work I have done on this car. Sigh!
So the first thing to do is to get the car warm and get it on the mark of the cooler Mark h or hot or whatever after that's achieved and you notice you're not losing cooling or whatever couple hundred miles whatever it is see what you got check your plugs go from there
Sometimes these head gasket symptoms can be ignored for years if you only drive locally and gently and not in hot weather...
How many miles on it? Did it specify which cylinder? Last digit in P030X indicates cylinder number; for example P0301 is cylinder one. What work specifically? Thread title could be more succinct? Would you mind if I reported, asked the mod's to revise to something like "Misfire and coolant loss, suspect head gasket failure".
I cannot edit the thread title now. Prior work included EGR cooler clean out and replacing the water pump as well as the regular maintenance.
Did you also clean the intake manifold? EGR Pipe? EGR Valve? I am curious to get the comprehensive list just so we can see if all this time spent cleaning stuff may or may not be the silver bullet to preventing problems.
Understand. But as I said: the mod's can. Including the intake manifold EGR passages? And at what miles did you do this? What motivated you, just from what you've heard, or were there symptoms happening? Also, could you answer these, from my previous post:
There is no silver bullet to preventing hg problems on these cars. It seems to be age related as well as miles since we are starting to see 100k mile hg fails when a few years ago it was 175k miles and above. We see plenty of clean free flowing egr systems with a hg fail. Certainly cleaning and replacing misfire related parts will not fix a failed hg. In this case the op should take it to Hybrid Pit for an early diagnosis and recommendations. Waiting just guarantees a higher bill later on. I always suggest a rebuilt engine, ideally one the never experienced an overheat or hg issue. A rebuilt engine includes pistons and rings.
Where some of these clean EGR’s done on the heels of head gasket failure symptoms starting. @ASRDogman is a canary in the coal mine who’s on orig head gasket, closing in on 400k miles IIRC, and proactively cleaning the EGR.
P0303 Cylinder 3 misfire multiple times was the code. Mileage was 153k. All the EGR circuit was cleaned out. from cooler to intake manifold. But, the car was run in very high temperatures for several days in Palm Springs, which probably sealed its fate. These cars use a gasoline engine block (Otto cycle) to run an Atkinson cycle engine. The Otto cycle engine uses an 8.6:1 compression ratio and was designed to cool that. The Atkinson cycle engine uses a 13:1 compression ratio, which is at the bottom end of the diesel range. The engine does not have the power and torque of a diesel, but at 13:1, it has the flame-front temperature of a diesel engine. Toyota added the EGR cooler, which is commonly used to cool diesel engines, to keep the temperature down. When the EGR cooler plugs up, you get a lot more temperature cycling of the engine, which crushes the head gasket. The aluminum head and block have a much higher coefficient of thermal expansion than the steel head bolts. The head gasket is caught between them. RIP Head Gasket!
Thanks for this information and good summary on your theory as to why head gasgets are failing. I appreciate your take on things. Do you have a theory as to why yours failed even though the EGR system was never pluged? You state that the "car was run in very high temperatures for several days in Palm Springs" but I dont know if high ambient temperatures would have that much of an effect on things?
That story leaves out something absolutely fundamental about the Atkinson cycle. What makes it the Atkinson cycle is that the compression ratio and expansion ratio are different. The Prius engine has a 13:1 expansion ratio. It does not have anywhere near that as a compression ratio, and such comparisons to diesel engine conditions are off the mark.
