Sheared water plug on block

[gregg_a_g]

So, I was removing the 1/4-20 plug on the engine block (250 inline 6) to drain water from the block. I thought the plug was backing out, but then I noticed that it has sheared off
about 3/4 of the way in. The top 3/4 of the plug came out fine, but the bottom 1/4 is still
in the block. I am going to try and use an extractor to remove it, but I am unsure if it is
safe to first apply heat and quench to loosen corrosion. Would heat and quench possibly
damage (crack) the block? Should I just use penetrating oil and the screw extractor
without heat?

 

[Bondo]

Ayuh,..... Do you mean 1/4" pipe,..??

There are no 1/4"-20 plugs in the block,.....

 

[gregg_a_g]

I was thinking about another part with 1/4-20. Yes, 1/4 npt plug.

 

[Bondo]

Ayuh,..... Just drill a hole through it's center, 'n try to back it out with an easy-out,.....
If ya wanta heat, 'n quench it, do it after ya drill the hole through it,.....

Once it's out, get a plain ole brass 1/4" pipe plug for it,....

 

[Scott06]

So, I was removing the 1/4-20 plug on the engine block (250 inline 6) to drain water from the block. I thought the plug was backing out, but then I noticed that it has sheared off
about 3/4 of the way in. The top 3/4 of the plug came out fine, but the bottom 1/4 is still
in the block. I am going to try and use an extractor to remove it, but I am unsure if it is
safe to first apply heat and quench to loosen corrosion. Would heat and quench possibly
damage (crack) the block? Should I just use penetrating oil and the screw extractor
without heat?

its a 1/4" npt plug not 1/4 -20 . Be carfeul with the excractor as they can snap off in there. Yes I would apply heat as long as you dont go nuts with it you will be ok.... Worst case just drill it out and retap with a pipe tap.

 

[gregg_a_g]

Yes, since the plug was "stuck", I'm afraid of the dreaded "broken extractor". It seems like it's easy to "over torque" the little parts if not really careful,
I couldn't tell that the plug was shearing!
If I have to "drill and re-tap", I guess I would have to go to 3/8 npt? Or do you mean try and drill it close without damaging the threads and then try to "re-tap" the little bits left over? Never done that before!

 

[Rick Stephens]

If that's a steel pipe plug I wouldn't even bother with using an extractor - just drill 7/16" and chase with a 1/4NPT tap.

 

[Scott Danforth]

I normally drill two 1/8" holes, just off center of each other, then turn that into a slot. then drive a screw driver into the remainder of the plug and back out

 

[Bondo]

Yes, since the plug was "stuck", I'm afraid of the dreaded "broken extractor". It seems like it's easy to "over torque" the little parts if not really careful,
I couldn't tell that the plug was shearing!
If I have to "drill and re-tap", I guess I would have to go to 3/8 npt? Or do you mean try and drill it close without damaging the threads and then try to "re-tap" the little bits left over? Never done that before!

Ayuh,..... Are you absolutely Sure it broke off,..??
I've seen crud build-up behind a pipe plug, that looked like iron, but crumbled to dust when tapped with a punch,.....

If it is part of the plug, be careful drillin', 'n tappin', as the back wall of the block, ain't that deep,....
Probably an inch or less, behind the hole,.....
I have 1/4", 'n 1/8" pipe taps, that I ground part of the tips off of, just so they'll cut the threads, but not crowd against the back wall of the castin',......

 

[gregg_a_g]

Yippee! Thanks, everyone. Yes, I'm sure it was actually sheared off. I figured the wall was very close to the end of the plug, so I was very careful. The bottom part of the plug did pretty much fall apart. I used just a bit of heat from a #4 welding tip (not a rosebud) to loosen it up. Then the last bits came out with the fat edges of straight screwdriver. All cleaned up and I found a 1/4" brass plug with the little valve on the end, like you see on radiators. So next time I need to drain it should be a lot easier. I was surprised how much water was still in the bottom of the block. I think the
last 1/4" of plug was another source of leak in my air pressure test.
I've got it charged back up to 15psi and am waiting to recheck in about an hour.

 

[Scott Danforth]

Use a plug. You cant probe a petcock with a pick to make sure its drained

 

[Lou C]

With the metal drain plugs I always use a bit of OMC gasket sealer or Permatex Aviation on the threads, they never seize up that way even with salt water use. You really do have to ream out the holes sometimes though, I had a 90* fitting on my V6 on the side with the starter (to clear the old bigger direct drive Delco starters) and these will clog up unless you dig them out with a pic.