Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

Removing Radiator Vent Plug

MaTTyBiGsMaTTyBiGs Posts: 26Member
edited February 25 in Strictly Steam
Hi all, just purchased our first home and it has steam heat. I'm working my way through everything that I can (stocked up on some of Dan's books) and it brought me to a question (first of many I'm sure, but starting easy).

Many of the vents on the radiators are quite old, and I am replacing them all and starting fresh. I need to re-tap some of the holes which I'm comfortable with, not my first time - and I've done some research on this. Some of the vents are not in the middle location (taking this from the book) so I wanted to fix this. This brings me to my question...

Any tips or tricks to remove an old plug that is where I want to put my vent? Is this a hopeless exercise? You can see the vent location in the picture and then the plug below that.


  • JUGHNEJUGHNE Posts: 6,224Member
    IIWM, I would cut the paint around the plug. Multiple applications of PB Blaster or Kroil over several days.
    Neither will smell good on hot iron, so maybe wait for spring.

    Doubtful the screw head will get it out, but who knows.
    Then carefully center punch and drill out in stages.
    Easy out might turn it. Not a lot of depth in the tube so caution on length of easy out.
    It doesn't look like there is room to add 1/4" X 1/8" bushing, so maybe only one shot.
  • mroberts5mroberts5 Posts: 72Member
    edited February 25
    If I was doing it:

    1st clean ALL paint off.

    If the screw head is proud of the radiator, I would cut the screw thread a little deeper to get more bite.

    Soaking it will help. I'd probably apply with a brush 2-3 times over 1-2 days.

    Make sure your screw driver fits perfect. An "hand impact driver" can help.

    I might try to apply some heat w/ a torch - it does wonders to crack all the crud in the threads.

    If you do drill, take great care to get a good center.
  • MaTTyBiGsMaTTyBiGs Posts: 26Member
    Thanks for the feedback, I will start by removing as much paint as I can and hitting it with some PB blaster for a few days. I need a bigger screwdriver to fit in there, so I may try that after a few days of soaking it. If that doesn't work, I'll try some heat and as a last resort - drill it out.

    If I do have to drill, what size bit would you start with? According to the tap I bought I'll end with 11/32".
  • mroberts5mroberts5 Posts: 72Member
    I'd start w/ an 1/8. Make sure you use NEW bits or bits you KNOW are sharp.
  • JUGHNEJUGHNE Posts: 6,224Member
    I would not drill it out the way out to the 11/32, that is for tapping a new hole. If you go that large I think you would leave part of the steel plug in the cast iron.
    I would go maybe 3/16 and try the easy out.
    If enough of the screw plug sticks out you might carefully cave it in after drilling, it would unscrew then almost by hand.

    I believe you want to preserve the existing threads and not try to create new ones. Clean up with tap, but not too deep, don't want to cut new ones deeper and lose the taper of the hole.
  • 1Matthias1Matthias Posts: 136Member
    I'd go after it with generous quantities of WD 40 (Or 50/50 acetone ATF) over several days, with the system still running to heat cycle the plug and hopefully draw the WD into the threads. Then I'd go after it with an impact screwdriver, and if that didn't work, drilling and an easyout as a last resort.
  • MaTTyBiGsMaTTyBiGs Posts: 26Member
    Good points, I forgot that it's already tapped at 1/8" NPT so that would not work out well.

    @Chris_L - do you mean in combination with an impact or just the easy out in general?
  • Chris_LChris_L Posts: 146Member
    MaTTyBiGs said:

    @Chris_L - do you mean in combination with an impact or just the easy out in general?

    I've never heard of using a screw extractor with an impact driver.

    In my case, I was doing it by hand trying to get out a sheared off vent from the hole. The easy out I used was too big, and as the tapered thread went in, it hit the radiator. At that point, I was trying to expand the vent hole, and... crack :(.

    If you don't mind damaging the paint, I'd put a torch to it before trying to trying to unscrew the plug. If that doesn't work, and you are really careful abut drilling in the center, I'd make progressively larger holes and then either collapse the remains of the plug or clean it out with a 1/8 inch tap.
  • MaTTyBiGsMaTTyBiGs Posts: 26Member
    edited February 26
    Thanks for all the input everybody, feel like I have a pretty good plan of attack now in an order that makes sense.
  • 1Matthias1Matthias Posts: 136Member
    Chris_L said:

    Then I'd go after it with an impact screwdriver, and if that didn't work, drilling and an easyout as a last resort.

    I would not suggest using an Easy Out. It is very easy to crack a cast iron radiator with one.

    Don't ask me how I know this.

    As I said, those are my absolute last resort after at least a good half to an hour of swearing.
  • ratioratio Posts: 2,136Member
    I wouldn't want to use the hammer-type hand impact on that, I'd be worried about cracking the tube. I might try a li'l ¼ cordless impact with a properly-fitting flathead bit in it, but lots of penetrating oil & heat as well. You won't get a lot of tries, I suspect.
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!