2014-15 head gasket problems?

mid 2014 saw updated pistons and rings. whether that fixed the egr/head gasket issues is unknown.
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Pistons and rings were revised to be less prone to consume oil. There were also some mods to intake manifold and EGR valve somewhere a long the course of 3rd gen. I doubt any of this prevents progressive carbon clogging of the EGR passages, and that clogging goes hand-in-hand with head gasket failure.

Buy one with lower miles, not much over 100k if possible, and keep on top of EGR cleaning. Or go to 4th gen with revised EGR system, more or less immune to the clogging, and head gasket failure.

 

I have a 2015, and when I did my EGR system a few months ago, it definitely was clogged. The rest of the system was still OK, but still needed a good cleaning. Even the intake manifold had a small pool of oil near the MAP sensor. So, while the 2015 may have revisions, the common GEN 3 issues still remain, albeit perhaps a little less problematic.

One thing I can say is that after cleaning the EGR system, my engine temps appeared to be much more stable (I use a Bluetooth OBD2 reader to monitor it). From my understanding, the huge fluctuations in engine temps is part of what leads to head gasket failure.

 

I know a couple of people here have said the same, and they got ganged up on quickly with the opposition saying engine temp wild fluctuation has nothing to do with head gasket failure. One more point for their team

 

If 70k mile 3rd gen is within your reach you’ll be good. Clean it first by 100k at the latest, then every 50k thereafter would be prudent.

 

Traditionally overheating is a significant head gasket risk. Warping of the cylinder head is often found. It is as much a quick change in cylinder temperature as anything else and the 1.8L is no different.

Thermal cycling in gen3s is a significant factor. I have logged 50f swings after full warm up in the same drive session. If you are in city traffic without the ac compressor running (like in winter) the engine will cool fast. Even when the battery gets low the engine only partially recharges it and does not fully raise the temp. Return to speed and the engine rises to 195f-204f.

Certainly increased carbon and oil buildup in the manifold is a factor. But not necessarily the cause. Interestingly, Corollas with the same engine design do not see abnormal head gasket failures.

Gen4 has significant changes in the cylinder cooling including addition of an insulator. The egr pickup is after a cat and the egr cooler is physically bigger for less restriction.

 

I have a 2015 trim 5 prius and my HG went out at 130-140k. I would say its less risk for 2015 models but it still would happen. Other than that i didnt have any oil consumption issues

 

but that doesn't explain gen 2

 

Definitely seems like a combination of issues contributing to the HG failures. I've seen a few mentions here and around the web about the gen 3 engine coolant ought to be changed earlier (around 80k). I'm wondering how the upgraded gasket in some rebuilds will hold up after time and miles, it might give a better clue if anyone still cares at that point.

 

Coolant temperature will drop faster rolling down a long hill in cold weather with fuel shut off than it will in slow traffic, because more air is coming through.
They wouldn't have bothered developing those cooling refinements if the 3rd-generation version hadn't been so vulnerable to thermal cycling.

EGR clogging may well be a factor, but it clearly isn't the only factor behind gasket failures.

 

Best bet might be a rebuilt engine. Plenty of posts around here if you do a search, and HybridPit in Buena Park CA does great work.

 

I believe they ship within states for free if you have can find a local installer. @GregC1979 would know.

addendum:

I have this “theory”, keep the EGR passages clear, and the head gasket will be fine.

see first 2 links in my signature. If on a phone, turn it landscape to see signature.

 

HybridPit uses an upgraded head gasket so it might last longer in the long run, but if the prices are similar I think you can't go wrong at this point. I might lean toward the rebuilt if you wanted to drive yours for an additional 150+ miles, just to have the upgraded HG.