Bubbles for an hour = breached head gasket.

You will not see oil and coolant mix unless there's detonation that cracks the cylinder wall.

Smoke out the tailpipe is dependent on how bad a breach is and yours is not pulling enough into the cylinder to create smoke/steam out the pipe.

This could have started with a small leak, or over time enough water evaporates out and the cooling system ran low. Could also be a bad radiator cap caused the issue. Aftermarket thermostats are bad news; they don't let enough coolant pass or they work sporadically.

Stay away from the one that said the water pump was the problem.

When it's repaired, and if you have the means it's not a difficult job, get an OEM, Mahle or AISIN thermostat, OEM cap, good coolant, MLS head gasket kit, but not FelPro.

You'll need 8, 10, 12, 14, 19, 22 mm sockets, ratchets, extensions, breaker bar, large pry bar, something to hold the crank pulley still to break the bolt loose, torque wrench in lbft, angle drill with cleaner pads, floor jack, engine hoist, oil absorbent and patience.

Get a spill free funnel for filling and burping the engine after it's back in.

FSM can be had here: [Moderator - link has been removed; we've recently been routinely removing such links to factory service manuals and other copyrighted materials because of IP concerns. It's quite all right to post just a few pages to help someone out however - just not the entire manual. Thank for your understanding.]

Otherwise, your looking at $2-2500 for a shop that knows what they're doing to do it for you.

❤ Head Gasket Kit for Subaru Outback & Legacy 2.5 SOHC EJ Motors 2010-12 OEM | eBay

This seller has links to valve cover gaskets and head bolts in his description. You can reuse your head bolts, or replace them.

 

The above information from Cardoc is the best information you will get anywhere.

Cardoc does these jobs all the time at his workshop and knows what works and what to avoid.

I changed the title to better describe the problem

Seagrass

 

Thank you kind of needed to hear something other than it's the hg because subaru is known for them I definitely didn't want to consider that kind of work just because they are known to have some hg issues on their vehicles because hg isn't the only thing that causes those issues. I flushed my coolant and I'm still seeing copper particles went to advance auto guy working had exact same problem turned out previous owner used copper radiator stop leak and it was causing some other issues. Told me to replace radiator hoses and do a combustion test because not knowing the full history there they could have caused some hg problem. Everyone around here so far has quoted me an estimate of at least $3000 possibly more for the hg repair so I have 2 people who have done their own before I will be asking if they mind assisting me.

 

Subaru engines are not like most other engines (I am guessing you have already realised this).

It is quite common for a Subaru engine to pass an exhaust gas in the coolant test even though the engine has a failing/failed head gasket. As Cardoc said above it is also not common to see smoke in the exhaust or the coolant and oil mixing.

One of the most common symptoms of failing/failed head gaskets in a Subaru EJxx engine (the type fitted to your 2011 Outback) is a continuous stream of bubbles in the radiator AND overheating.

The head gasket in an EJ engine has a coating that fails and this prevents the head gasket from sealing properly. Your 2011 vehicle was fitted with MLS (Multi Layer Steel) head gaskets at the factory and is therefore less likely to have a failure BUT in the last 12 months or so there have been several reports by forum members that their 2011/2012 vehicles have head gasket problems. From memory these vehicles had travelled 165,0000+ miles.

As I suggested above the information that Cardoc gave above is the best information you will get as he works on these engines often enough to have first hand information.

If you do replace the head gaskets please ensure the replacement parts you use are quality parts as most of the cheap parts are not worth using. The parts Cardoc linked in his post are the ones I would recommend you use.

Seagrass

 

When you fix it, while the engine is out, flush the heater core.

 

Cardoc and Seagrass have it nailed. My proof is my own story. Check my post history, it reads almost exactly like yours. Aisin kit for timing belt and water pump and a quality set of head gaskets and you'll more than likely be a happy camper.

If you have the time, space, and tools you can do most of the work yourself, minus any machine or valve work needed.

Since mine happened during early Covid I had the time. In a house so had some garage space to work with. Kelt my eyes open and picked up a shop crane / engine hoist and engine stand off Craigslist for great prices, along with a few other tools I needed to do the job. All in, with all parts and tools my cost was right around $1000 in 2020 dollars. Took my time, made sure every thing was clean, clean, clean upon reassembly. Replaced other various seals at that time as well, just because they had almost 100k miles on them and easier to do on the engine stand than in the car.

 

Ok I just bought a 2011 subaru outback a few months ago and a month and half ago started overheating thermostat was stuck closes boyfriend changed it boiled it in water still good. Did fine a few days started again he thinking hg but maybe water pump another mechanic said it's the water pump no way at all is it the hg. So now I buy a water pump and pay mechanic almost 500 to put on he also replaced the new thermostat because apparently it was stuck closed. Now 2 days later hose from radiator and overflow tank starts coming off every couple days so boyfriend said it's still good and clamped it on. Did ok for a bit then I start noticing bubbles in overflow tank and now for the last 2 weeks my overflow tank keeps filling and overflowing bottom hose staying cold I see it could be clogged radiator by now I'm fed up with being pulled around because now everyone keeps saying without looking it's hg just because subaru is known to have hg issues. So I just learned to flush my radiator clean my overflow tank but I tried bleeding radiator but it's like endless supply of air bubbles without cap overflow stays normal thermostat opens and closes and no overheating but after an hour I still had air bubbles coming out I gave up put cap on and overflow tank starts to receive coolant and bubbles so I shut car off. Now my car has had no smoke motor is nice and quiet until it starts to overheat there was no oil in coolant no coolant in oil the white stuff under oil cap no check engine light no misfires and the bubbles under radiator cap look like boiling bubbles they are not frothy looking there has been absolutely nothing else indicating hg except air and overheating which can be many other things. If I have to learn to replace hg I will but want to see if anyone else has experienced this issue or have an idea what it may be other than hg. Or maybe tip on actually getting air out. My car doesn't have bleed valve or screw so had to bleed from radiator. I read a few say air can circulate back in through funnel to cover top but nothing else said to cover the top.

Dealing with it now too... Pressure building in coolant lines... holds thermostat closed. Put a few holes in thermostat. Still getting the ECT P0117 code.

 

Doubtful. Who drills holes in their thermostat?

 

Maybe it’s a Subie thing. I ran a performance shop for 10 years and never came across a drilled thermostat. Most guys just use a colder thermostat.