Ive read plenty of the posts on this but I'm still having issues, had an air bubble so I bled it, then the lower hose was cold and firm so I changed the t stat (with Subaru part) bled again did the upper heater hose trick and vent on radiator. The overflow tank is filling up with coolant and I continue to get air. I did a block test, I did it on the overflow tank and got nothing fluid stayed blue, then I did it on the radiator and with the vent in and overflow tube plugged there's no air in the system, the bulb will barely expand on the tester, but I did it for about 5 minutes and fluid stayed blue, I think I heard some gargling by the radiator cap, I'm replacing it and putting a clamp on the overflow tube to see if that's where the air is coming from. My question is where do I do the block test at? The rad barely sucks air, which makes sense because it's a sealed system, but will the overflow tank even work? Also what else should I check?