Drained heating system to replace rad valve - can't refill

[157]

• 3 story (2 main floors plus attic with two rads), 1920's house
  
• 14 total hydronic radiators
  
• Single zone
  
• Gas-fired Crown boiler (see pic below)
  
• Manual (?) cold water refill (see pic below)
  
• Has expansion tank on return line (see pic below)

I had a leaking rad valve on the first floor. I drained the system and replaced the valve. Now, I'm trying to refill the system and I cannot seem to get the heat past the first floor. By the time I get the last of the (5) first-floor radiators bleed and shooting water instead of air, the pressure in the system is so low that the next radiator I open starts sucking air (see gauge pic below).

Here's the order of operations I'm following:

1. Turn the system off (flipping off kill switch, but leaving pilot on), let it cool down
   
2. Turn on the manual cold water refill to bring the PSI up to ~12 (the gauge half-works on the boiler, but the expansion tanks starts spitting water at some point)
   
3. Open the bleeder on the first-floor radiator furthest away from the boiler and work towards the radiator closest to the boiler
   
4. [Lost pressure]

Is this where I should have more patience and just go back to step 2 and open the manual cold water to refill and start over? At this rate, it will take me like 5 hours to get all three floors bled — there's 10 more radiators to go on floor two and three!

Full boiler setup:

Expansion tank on return:

Gauge after bleeding first-floor radiators:

Cold water refill setup:

 

[Fitter30]

Your boiler is 160*? Your tridicator gauge is bad if it not. The water regulator is bad if system doesn't fill. Auto air bleed on ex tank needs to be replaced. Fill system to 20 lbs then bleed some radiators or use two people and your phones for communication. Check the ex tank air pressure while system is drained. Working on a system with a bad gauge makes diagnoses a lot harder especially if the person doesn't know it.