Subaru Repair: 98 legacy wagon still hot after headgaskets done, pin hole leaks, head gaskets

Question
Hi, i have a question about my 1998 legacy wagon. I am a "B" tech but no longer work in a shop. I picked up this car cheap because it overheats- previous owner changed the thermostat but still got too hot. I changed the cap and thermostat and it still got hot. I read how many subarus need headgaskets so i decided to just do it (supposedly headgaskets can be hard to diag w/ pin hole leaks and not always showing up on pressure checks). Anyway, installed new updated head gaskets, resurfaced the heads/ checked for cracks, block looked good, new waterpump, new radiator. First startup i left the cap off, engine idled at 1500rpms, heat on high, slowly added coolant as needed, watched some bubbles come out of coolant. The temp gauge was below 1/2. So i let the car cool down, filled coolant as needed, put the cap on, let the car warm up and with out the heat on the temp started to rise too high. With the heat on temp stayed near 1/2. The lower hose barely got warm, cold even... even though the gauge is reading hot. When i drained the cooling system i only used a garden hose to flush the block. The only thing i can think of is that i need to get a real flush done by a shop. Possibly some of the smaller smaller passages clogged. Or is there still air in the system? I thought about bypassing the heater core to see if that is clogged but i figured the coolant is circulating thru because that keeps the temp down. And the fans come on like they should. So i am stumped, is there anything else i should do to get air out?  

Answer
After you replaced the radiator, did you refill the radiator with coolant with the air plug still in? If so, your cooling system may have an air pocket, which may never bleed out unless you use the Subaru method listed below. .
By the way, the air vent plug is at the top of the radiator, on the passenger side of the radiator, and is a black plastic plug with a phillips head. And, make sure the radiator is fully cooled before you try this.

FILLING OF ENGINE COOLANT
1) Remove air vent plug from radiator.
2) Fill engine coolant into radiator up to filler neck position.
3) Fill engine coolant into reservoir tank up to upper level.
4) Attach radiator cap and reservoir tank cap properly.  
5) Install air vent plug.
6) Warm-up engine completely for more than five minutes at 2,000 to 3,000 rpm.
7) Stop engine and wait until temperature drops to a safe level.
8) If engine coolant level drops in radiator, add engine coolant to filler neck position.
9) If engine coolant level drops from upper level of reservoir tank, add engine coolant to upper level.
10) Attach radiator cap and reservoir tank cap properly.

This method usually works. Good luck.