[cardoc]

Whenever I drain the coolant for any repairs, which is a lot, when I refill the system, using the Lisle funnel, I will idle the engine for about 5 minutes. I don't bother with jacking up the front of the cars. At 5 minutes idle, I snap the throttle a couple times to 4k rpm, turn the heater on full and blowing out the upper vents to verify flow through the heater core. No heat, snap the throttle until I have heat. The quick rpm change pushes coolant through the system with more force and moves air out.

I then let it run for 10-15 minutes and keep an eye on the funnel. When I don't have any bubbles and only a little flow of steaming coolant, I shut it off and let it cool down, usually over night. As the coolant contracts the level in the funnel will drop. Next morning I take off the funnel and put the cap on. Done.

You would have to start again with the funnel. Not just to insure air is out, but also to check for a HG issue. Set it up like you did prior. Fill the funnel to half way and start the car. Let it idle to get the temp up and check for even heat out of the vents. Snap the throttle a couple times and watch for bubbles at the funnel. Keep watching the funnel for bubbles as it runs. If you have a scan tool, have it set to watch the temperature. If it gets close to 225°F, turn it off and let it sit. Let it run until the fans come on and keep watching the funnel and temp. If after the fans kick on and you are getting air bubbles, you may have a breech.

 

[cardoc]

The level will rise. Normally about an inch or so. When you snap the throttle the force of coolant being moved pushes the coolant to the funnel and the level will rise and go back down. As coolant expands with heat, the level will rise slowly and steady out until air escapes.

If it's rising substantially, like more than 1.5" and continues to rise, then that may be a problem. Air is accumulating in the engine and pushing the coolant up. If it does this, then you can snap the throttle again and wait to see if air bubbles emerge.

The lower radiator hose will be at the temperature the coolant in the radiator is. The engine pulls from the radiator at the bottom. Coolant flows out the top hose, so when it's up to temperature then it will be hot. When the temperature in the radiator starts to get closer to the engine then the lower hose will be a bit warmer.

As far as the heater core goes, you put air pressure on the coolant system via the radiator fill neck, not too much, no more than 16 psi, and watch for coolant to leak out the HVAC drain. Also listen for the leak from inside the car. It may take a while depending on the severity of the leak, if there is one.

Gurgling noises from behind the dashboard can also be one of the electric motors for the HVAC.

 

[cardoc]

I suggest you do not put in a "leak sealer", "HG Repair" liquid, or other substance in the engine. It will only make it worse and lead to replacement of other parts. Radiator gets restricted, coolant passages get restricted, thermostat gets F'd up, possible heater core gets gummed up. That crap is just that, crap.

Parts list for head gasket repair should include EJ255 head gaskets with the normal EJ253 gaskets for the valve covers, tube seals, cam seals if you want to change them. May as well do the timing kit while you're at it unless it's been done recently. AISIN Kit with Japanese parts, (KOYO, Mitsuboshi, w/AISIN water pump and metal gasket).

 

[cardoc]

I will tell you that I am not too enthused with FelPro gaskets. The valve cover gaskets tend to leak due to ill fit. The HGs are questionable.

With the MLS gasket upgrade I suggest you use the turbo torque settings on the head. Those last couple turns are important to insure a good seal. Watch the temp while you burp it and after you put the cap on the radiator. If it runs hot or has signs of gasket seepage, retorque the heads.

 

[cardoc]

That is the correct part number for the EJ255 MLS gasket. I use them all the time without issues.

Like I posted above, use the WRX head torque specs.