2011 Prius head gasket problems!

welcome!
how many miles? it is about the same work if you can replace it with a low mile salvage.

you can try the sealant, nothing to lose that i can think of.

 

It all depends where the gasket is compromised. If it’s leaking into the cylinders, you’re in deep trouble. If it is just leaking externally you might get away (temporarily) with some sealant. In any event, it ain’t gonna fix itself. Not knowing how many miles are on the engine, it would be very hard, (without tear down) to suggest a direction you should follow. My way of thinking would be to remove the head for inspection and go from there.

 

How long ago did the headgasket fail?

 

2011 Prius, blown head gasket at 209,000 miles. Check Engine comes on, cylinder misfire, and then the temp light comes on with no anti-freeze, and the blue, sweet smoke from the tailpipe. Did the liquid sealant on the gasket, and it cleared up the cylinder misfire and burning antifreeze, but car still shook terribly. Checked the Transmission fluid, and it was black. Flushed and refilled (no filter, so no pressure transmission change) and the car is running smoothly, and (almost) like new. Toyota told me in the beginning when I bought the car they don't recommend ever changing the transmission fluid. If that was true, how come it's not in a sealed compartment and why is there a drain and fill plug? Bottom line, change the transmission fluid, and the sealant works on the gasket! I am not sure for how long, but if I can avoid an engine swap for another 50,000 miles or more, then I'll be happy.

 

Rebuild it if it is not a warped block. If it is buy a used engine and rebuild.

Here is my Gen3 Engine Manifesto:

It is a bad design engine. The engine burns oil and has excessive liquid build up in the intake manifold. Flawed piston ring design was updated in mid 2014. Oil / condensate mix in the intake along with blowby fed to the cylinders via the egr creates carbon and preignition. Egr intake is before the cat on these years; gen4 egr intake is after the cat and therefore much cleaner. Thermal cycling is also a problem for the cylinders due to stop start and poor coolant passage design. Cylinder insulators and revised coolant passages remedied uneven temps in gen4.

Generally these factors create a head warpage that allows the coolant into the cylinder, particularly after a complete cool off. The coolant may or may not temporarily foul the plug. At first the engine heats up and stops the coolant loss before it is really noticeable except for startup rattling. The plug starts firing and the engine runs fine, typically for the rest of the day. People incorrectly think it is plugs, coils, injectors or clogged egr, even though it runs fine after a few seconds, wasting time and money. Heads must be machined with a head gasket job.

Occasionally the startup rattling and short duration coolant fouling may bend the connecting rod slightly. This is often unnoticed during a head gasket job, leading to a second failure a few miles later when the rod goes. Or the rattling is masked with a sealer allowing more time for the bent rod to break.

The engine to transaxle damper is just that, a short term slippage mechanism when the engine rpms are not exactly matched by the electric motors through the planetary gears. This slippage is the startup rattling you hear. There is no mechanical disconnect like you get with a clutch or torque converter.

The best solution to keep a 2010-2014 Prius running long term after a head gasket fail is to rebuild a used engine with revised pistons and rings, remachine the head, clean the egr cooler and then change oil after 5k miles rather than 10k.

By the way, a later model spin on oil filter housing will bolt on. A high quality oil catch can with sintered bronze filter is recommended on the pcv line but only if the owner can be counted on to empty it. The pcv intake was also revised on gen4.

Bottom line: This engine is a bad design starting with low tension rings, a bad egr design, a poor cylinder coolant strategy, a pcv intake too low on the block, 40f thermal cycling many times during a drive cycle particularly in stop and go or when excessively "idling", aggravated by the parts cannon and block sealers.