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Help with bleeding my boiler

Rongold Member Posts: 21
Hi all, New member here. I have a GO-6 Weil McLain boiler. The immersion well for the temperature sensor started to leak internally, and water got into the control box and shorted it out--filled the basement with smoke--blew the breaker. OK, no problem. I got a new immersion well and control box. I broke the well loose--not an easy job on a 20 year old boiler--it was TIGHT !!! All I have to do now is drain down the boiler and change the well and control box---BUT, the boiler has anti-freeze in it, as I have 1 zone that freezes up in the winter, so, how do I bleed the boiler without losing all my anti-freeze???

In the piping just before the 3 zone valves, there is an American Air Purger with a Taco 400 Hy-Vent screwed into in, as well as another Taco 400 Hy-Vent mounted to the pipe just next to the circulator pump. As far as I know these vents will allow air to escape while filling the boiler, but they lock up as soon as there is any pressure in the system--Am I correct ??? The zone valves are closed, and I have the valves in all 3 return lines just below the hose bibs closed, so when I drain the boiler the upstairs piping should remain full. I am going to refill the boiler manually with the anti-freeze I drained out, through the pipe that sticks up next to the circulator pump that one of the vents is attached to. That pipe screws into a high spot on the front boiler section. My problem is how to get the air out once there is pressure in the system. Is there such a thing as a vent valve that will eliminate air even when the system is pressurized ??? That would be my solution. I have enclosed a couple of pictures to show what i am talking about.

Thanks for any help that you provide, RON


  • Alan (California Radiant) Forbes
    If you can isolate the supplies (zone valves) and returns (manual valves), it should be an easy job to change out that well.

    You don't have to drain the boiler completely, just to below the level of the well.

    As far as I know these vents will allow air to escape while filling the boiler, but they lock up as soon as there is any pressure in the system--Am I correct ???
    These vents will release air at any pressure.

    With the setup you have, I would change out the well and at the same time, change out all those Taco HyVents, especially the one on the boiler. They tend to fail after a few years. Refill the boiler to full working pressure then open the isolation valves. Those vents will get rid of most of the air; the system should operate and over a few cycles, the remaining air will get vented.

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Rongold
    Rongold Member Posts: 21
    edited May 2021
    Thanks for the reply Alan. The vent in the American Air purger is only a few months old. The one mounted on the pipe is OLD---Probably 20 years old. I have another brand new one for that spot. I thought that once liquid under pressure got into those vent valves the air would no longer vent out. Are you 100% sure about that, as that would solve my problem if they were capable of venting under pressure. I may wind up dumping the whole system, because the liquid that seeps out of the immersion well is quite brown. The boiler anti-freeze has been in there for about 15 years. Is one brand of air vent better than another ??? Are they all OK with boiler anti-freeze ??? Thanks for any other info you can give me.

  • Ctoilman
    Ctoilman Member Posts: 105
    15 yr old anti-freeze?   Has it been checked for pH as well as freeze point?  I'd expect all new anti-freeze will be necessary to do a correct repair.  No doubt change the air vents as well, they all fail after a few yrs, no matter what the brand, basically buy the least expensive you can get.  
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    Looks like you have a condensing issue in the flue and may be underfired, or poor draft due to plugged/partially plugged flue/heat exchanger.

    There was an error rendering this rich post.

  • BDR529
    BDR529 Member Posts: 289
    Since it was shipped with the circ in that location I'm gonna leave it right there.
    EBEBRATT-Ed Member Posts: 15,616

    After 15 years the antifreeze has done it's job. I would drain the antifreeze and flush the system good a couple of times then fill with water to a pressure slightly more than you run at. maybe use a neutralizer

    Fix any air vents and anything else that is questionable

    Then refill with antifreeze

    Old antifreeze can cause issues
  • mattmia2
    mattmia2 Member Posts: 9,740
    The automatic air vent has a chamber and a float. if the chamber is full of liquid the float closes the vent. If there is air in the chamber the float falls and opens the valve to let that air out.

    The well likely failed because the antifreeze wasn't maintained and has become corrosive.

    Depending on how you put the antifreeze back in you may need a pump to put it back in, like a bucket or trash can with a submersible pump in it.