Bubbling in overflow, many repairs to fix it

[cardoc]

Don't trust the shop. I have had many cars come in where the owner says the dealer did this and that or another shop prior put in OE parts and I find aftermarket. The number on POS used by these shops is MotoRad. When you pull the thermostat; if its a MotoRad, it will be stamped on the side. A Subaru stat is much larger when compared to an aftermarket.

And are you losing coolant? Level going down?

[1 Lucky Texan]

[novakdesolation]

I will try to pull the thermostat in a bit, its pretty cold here for me so not sure if I will be able to today, but I do want to start it up again and see if I can smell exhaust from those bubbles. And yes I have been losing coolant but only from the overflow as far as I can tell. The overflow was spilling out during the emissions and part of the drive home up until I stopped at the gas station

[cardoc]

If there is a blown gasket that is allowing for combustion gases to get in the engine, then the coolant can get into the combustion on the intake stroke and you will smell it at the exhaust pipe.

[novakdesolation]

I haven't smelled anything like that in the exhaust, but am trying to pull the spark plugs to see if I can find any signs of coolant

[novakdesolation]

also did not happen, way too cold for me [lifetime resident of phoenix moving to colorado was a big difference] but thanks to your guys' help, i believe it has been narrowed down to the thermostat, the HG or the head itself. i'm leaning to the head gasket, but the shop owner that gave a warranty on the head gasket will not honor it at this moment because he believes it's a warped/hairline cracked head or cracked block. i just think he doesn't want to work on it for free. i will keep reporting back as i find more information and a conclusion to the story

[punt speedchunk]

If you're getting combustion gases into the cooling system, the upper radiator hose will generally be very firm if squeezed. It should have some give to it if the system is operating normally. I've also seen cylinder pressure hold the t-stat closed on cars with bad internal leaks.

[novakdesolation]

The tstat would make sense, as it seemed like the problem would go away on its own after shutting off the engine.thanks for the info!

Edit: see below. I believe the thermostat may be part of the problem unless its being caused by the exhaust leak. But I can ascertain that there is exhaust coming through, when I had to stop in the post below, I checked the overflow, and exhaust came pouring out like fog.

[novakdesolation]

The hose is very firm, but the leak temporarily stopped [no bubbles coming up at this moment, not overheating] I took a 14 mile trip and at 7 miles and 8 miles I had to stop because it spiked and I turned it off for 2-4 mins and it was fine. My question is [and I know its hard to answer] is since the bubbles do not happen constantly like the overheating, is that more likely a head gasket than the head being cracked?

[burnout8488]

Did you have the cylinder heads checked for flatness at a machine shop? You said it was overheated at some point.

If the head gaskets were replaced with the multi-layer-steel gaskets (MLS) (which they should have been), the coolant conditioner wouldn't be necessary anymore. Were they replaced with steel, or the old style gaskets that will eventually fail again?