Removing a Pipe Plug

I want to remove a pipe plug on my Cummins 6BTA5.9 M3 370. It is adjacent to the thermostat housing and forward lifting lug....see photo attached. I THINK it is a 1/2" NPT plug; it has a square drive socket head (3/8"??...not sure).
It hasn't been touched for 17 years. I put a ratchet socket wrench with an extension piece onto it but the ratchet was going to break before the plug moved.
What are the 'trade secrets' for getting this thing out?

Start by spraying it with penetrating oil, tapping it with a hammer and letting it sit for a few hours. Repeat if necessary.

A breaker bar is better than a ratchet. It's cheaper and less likely to break. An impact wrench might help along with the penetrating oil.

Aquabelle said:

What are the 'trade secrets' for getting this thing out?

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Generous dose of PB Blaster 1X daily
Helps to drag a pin along the top of the threads to get rid of rust and allow penetration.
Very very light application of some heat via hair dryer to help penetration (optional)
Make sure key fits snugly in pipe socket. Proceed to either round off socket (or break ratchet) (It helps to tap-tap-tap end of ratchet w/ hammer)
Buy a lot of carbide drill bits
Drill holes in pipe plug. Start w/ small dia. Don't push or bend bits. Use plenty of lube oil.
When hole is large enough for EZ Out, bang it in enough for threads to grab
Put socket wrench on EZ Out and apply lot of down pressure w/ sideways torque.
Buy more carbide bits and bigger EZ Outs as required

It's actually easy to do and plugs come out quickly. Disadvantage to drilling is you end up with lots of metal chips inside. If you're handy with welder you could weld extension onto plug and avoid the drilling.

2nd what Wes recommended. Try moving it both ways, tight & loose. You do know the old mechanic's method of making a fastener tighter in order to get it loose?? Just so it moves, then loosen. It works.

I made a note bbased on several sources that the best penetrating fluid is a 50/50 mix of transmission fluid and acetone.

Couldnt see in the picture, but if coated in paint, try and break that connection first with hammer, heat, sharp object...whatever.

If you have access, an impact wrench does an easier job of removing plugs, nuts and bolts that are rusty, etc. Often an impact wrench will remove a bolt that would otherwise twist off it's head with a breaker bar, etc. You can rent impact wrenches at most rental stores.

If you are removing the plug to install an overheat alarm you may be better off using the temp sender hole and adding a nipple and a T fitting that will take both.

Thanks from a DIY-er to you tools pro's for the tips. Other Gary, I want to remove this plug to fit a 'spitter'...an air vent for the coolant system that will expel into the header tank. This is where is goes on later-model engines than mine.

There are proper and correct pipe plug/nipple removal tools (once you have damaged the fitting beyond normal tools) it involves drilling out to a size that matches the removal tool BASHING IN WITH A HAMMER and out the fitting comes, Just a big easy out really, but works really well

Cheers Steve

Forgot to say, most of these fittings are originally put in place with a locking paste (thread locker) so if the engine is hot it will help also the prudent use of a small flame (miniature hand held torch type) will also help , typically requires around 500 f to release the lock paste

Cheers Steve

impact gun will have it out in shore order.

Scrape any paint off where it is located , helps the oil get in and is one less fight to removal.

Use and impact driver with a big hammer.

Most folks think "PB Blaster" is the best penetrating oil.

A 1/2" breaker bar, a 1/2" extension and a 1/2" to 3/8" adapter has always gotten those out for me. Impact is a good idea, but never needed one. I doubt the penetrant will get into those threads past the red sealant they use.

I'd try penetrating oil, tapping with hammer, then after a couple of days an impact wrench. They are available battery operated so very convenient, try tighten direction briefly first, then hopefully it will back out.
Good luck

What's all the fuss for a 1/2" pipe plug? Stick a 3/8" extension bar of appropriate length, add a breaker bar and turn counterclockwise.

CPseudonym said:

What's all the fuss for a 1/2" pipe plug? Stick a 3/8" extension bar of appropriate length, add a breaker bar and turn counterclockwise.

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I think he is asking because he already tried that. He used a ratchet, not a breaker bar, but otherwise what you suggested. He is asking for suggestions because that didn't work for him.

X2 impact driver

High Wire said:

X2 impact driver

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My impact driver looks very different than that. Air impact driver with an air fitting on the end makes short work of many jobs. Runs off of Perter cable pancake compressor. Love it, but not used much.

Set it for CCW, hold it in place with a little CCW torque, and whack it with a 3# sledge. Works great if you have the room and the target is something sturdy like an engine block.

Heat and a hand impact driver as shown above.

Maerin said:

2nd what Wes recommended. Try moving it both ways, tight & loose. You do know the old mechanic's method of making a fastener tighter in order to get it loose?? Just so it moves, then loosen. It works.

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X2 to this!

If you haven't stripped it out yet, the absolute first thing I would try is to put some penetrating oil on it, take the boat at and run it at WOT to get the engine as hot as possible, shut it down, then try it with the engine piping hot. If you really wanted to get crazy I think there are freeze sprays you can get that you might try spraying on the plug. The engine will expand as it heats up, but so will the plug. The ideal situation is to get the engine super hot, and the plug cold. The heat will soften up whatever compound it was put in with too.

Well finally got it out! Repeat applications of WD40 over a couple days, gentle tapping and tight-then-loose technique and with a bit of muscle it came out cleanly. I replaced it with a 1/2" to 1/8" bushing into which I fitted a 'spitter' line to purge air from just behind the t/stat into the coolant header tank....works fine. Thanks for the tips and advice.

Good for you! And thanks for reporting it.