Seized Knuckle Grease Plug (1 Viewer)

[uscmas412]

I'm helping @SmokeSkiCA with his front axle overhaul (complete rebuild and first attempt for either of us). One of the knuckle grease plugs is seized and we've tried the below steps:

• Crescent wrench
• Vise Grips
• Stud remover
• Nut Remover
• Lots of MAP torch and PB Blaster

As you can see from the pictures, the plug head is rapidly becoming rounded. What options do we have other than learning how to weld?

 

[NLXTACY]

Drill a small hole through it and use a philips screw driver to turn it. Or anything that will fit and not bend. I haven't needed to do it myself but I was able to talk someone else of the ledge with it. He said it worked fine. YMMV.

EDIT: I had him heat it as well, the plug I mean.

 

[BigAxeJack]

Propane is not very hot, maybe step it up to Mapp gas or oxy/acetylene. Mapp is readily available for sweating copper pipe joints, in a yellow can.

 

[bajaphile]

How long have you used propane on it? I'd generally say, yeah maybe bring to a shop and they can heat with oxy-acetylene torch, but I'd be a little worried about warping the cast knuckle.

Drilling out the plug would be do-able as well...

In my experience, the fill plug isn't needed as long as you rebuild your knuckles every 5 years or so... you shouldn't be needing to add grease.

 

[-Spike-]

Heat, and a pipe wrench. Plan on replacing the plug.

You can always pull the ABS sensor to add grease, if necessary.

 

[-Spike-]

Heat, and a pipe wrench. Plan on replacing the plug.

You can always pull the ABS sensor to add grease, if necessary.

Also, for what it's worth, there's no reason to tighten those plugs more than a bit past snug.

Hmm, thought I was editing, oh well. Sorry for the double post.

 

[Rifleman]

Weld a nut on top of it, and be done with it. When you replace that plug, just as an FYI, it' NOT an American SAE PIPE plug, it is in fact a Whitworth pipe plug, and the two are NOT interchangeable.

 

[ajax1]

I always have had success with 10mm open end wrench, heat would be good

 

[Rifleman]

In the future when you go to remove that new plug your going to install, There is a special 8 point socket made just for removing square pipe plugs. Craftsman sells a complete set of 8 point sockets that covers almost all the plugs you'll encounter in automotive work. But since they started making all their hand tools in China, i stopped buying Craftsman all together. Here's a link to a nice set of Williams 8 point sockets, that are still made in the USA.
https://www.amazon.com/Williams-WSB...1516165032&sr=8-7&keywords=8+point+socket+set

 

[uscmas412]

After a bit of drilling and more heat, the stud extractor did the trick. Good to know about the 8 point sockets!

 

[Dave 2000]

I always have had success with 10mm open end wrench, heat would be good

Interesting, mine are 12mm perhaps a larger fitting, can't see why though?

Regards

Dave

 

[uscmas412]

Turns out we were using a MAP torch, apparently colors mean things?

 

[scottryana]

Yep, mine are 12mm as well.

Interesting, mine are 12mm perhaps a larger fitting, can't see why though?

Regards

Dave

 

[Malleus]

How long have you used propane on it? I'd generally say, yeah maybe bring to a shop and they can heat with oxy-acetylene torch, but I'd be a little worried about warping the cast knuckle.

Drilling out the plug would be do-able as well...

In my experience, the fill plug isn't needed as long as you rebuild your knuckles every 5 years or so... you shouldn't be needing to add grease.

FWIW, there's no danger in "warping" the casting. It's cast steel and MAPP gas burns above 3000°F, which is above the annealing point of cast steel. The concern is embrittlement. The casting is soft (meaning not heat treated) and the free carbon on/it it can react with the heated steel to increase the hardness. This isn't preferable on this part, since it is subject to impact loading and needs to be "squishy" (that's an engineering term).

I wouldn't heat the casting directly, heat on the plug would be OK, for the few minutes it would take to heat through the cross section. I would not recommend cold shocking the plug/casting after heating. Cast steel doesn't like thermal shock at all.

HTH