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I have been removing core plugs from an engine I'm rebuilding with varying levels of violence. The engine block is aluminium and I'd like to reduce the chance of of me damaging it.

How do I remove plugs while minimising the risk of damaging the engine block?

(example of core a plug... not my engine)

enter image description here

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  • I don't know much of anything. Why are you removing the freeze plugs?
    – Zach Mierzejewski
    Jan 27, 2016 at 18:30
  • I am replacing them with new ones. I probably should have made that clearer. As they're made from steel they can eventually rust and cause coolant leaks.
    – Sam
    Jan 27, 2016 at 18:53
  • Just take care if using a hammer and (chisel, drift, or screw driver) to tap carefully as you can by mistake drive the plug into the hole and have to fish it out. ---Hitting a screwdriver is not proper tool but used.
    – spicetraders
    Nov 26, 2016 at 22:27
  • The aluminum block will cathodically protect steel and prevent corrosion.
    – blacksmith37
    Jun 18, 2020 at 16:02

4 Answers 4

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This video confirmed what I was thinking.

You need three things:

  1. Flat tip screwdriver
  2. Hammer
  3. Channel locks pliers (or ViceGrips)

Take your screwdriver and hammer. Place the screwdriver flat along the bottom of the freeze plug. Hit the screwdriver with the hammer until the freeze plug "eye lids" (as the guy called it ... this is where the freeze plug basically tips over in the freeze plug bore and the top portion will be sticking out). Grab the top part of the freeze plug with the pliers and roll it out of its hole. Here's an image of what the freeze plug looks like when it's in the "eye lid" position and how to grab it with the pliers.

enter image description here

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  • Using pipe grips to lever them out looks like a good idea, although I might have to pack some card or something between them and the block.
    – Sam
    Jan 29, 2016 at 8:57
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Sometimes really corroded ones will not remove like that or there is a lip behind the core plug that doesn't allow that to happen.

Sometimes you can drill a hole in it and screw in a bolt with a self tapping thread, eventually the bolt will come up against the inside of the block and the plug will pull out.

Or you can drill a hole in it and insert a self tapping screw attached to a slide hammer.

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Proper tool is a freeze plug puller.
SNAPONS VERSION OF PULLER
You drill a small hole that the screw tip of the puller grabs and it then pulls the plug out.

While most common home mechanic use is the screw driver (bad tool for the job as you should not strike a screwdriver with a hammer).
If you must, use a drift or small chisel with the hammer. Just make your hits carefully as I have seen folks knock the plug into the block and have to fish it out.

The puller is normally found in the set with the proper insertion tools for reinstalling new plugs.

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In a tight engine bay, I've used an open end wrench with a hammer, it grabs the edge of the plug and turns it, so it can be grasped with pliers and pulled out. You have to find the proper wrench size, as it needs to be the exact one to dent the inside of the lip of the seal and grab it while hammering it to turn it.

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