Differential Fill Plug Rounded Out
 

Well, I have been doing some routine maintenance on the wagon. Today I was going to drain and fill the diff. Of course, prior to draining the diff I was going to make sure the fill plug came out. The PO rounded it out. I have the proper 14mm hex wrench, but it just slips when any pressure is applied. Is there anything that can be used to remove the plug? I do NOT want to drill it out. Thanx in advance for all of your help again.....

Clean the hole really well... like with Brillo pad and then alcohol ... also do that to the shortest bolt you can find which has the largest head which will fit into that hole.
Then mix up a small amount of the strongest epoxy you can find... JBWeld, etc... and place the bolt head in there and leave at least 24 hours without allowing it to move...... . depending on temperature...
Then take a couple of nuts which fit on that bolt and screw them onto it...and use them with a breaker bar to loosen it.
If you need to put your car jack into the hole on the right rear of the car...and attach a comealong to the breaker bar... this gives you a lot of force but in a controlled way.... not like an air wrench... I have posted pictures of that arrangement in the archives..

Leather's directions will work very well. If the plug is available as an orderable item, try taking the whole pumpkin cover off, do leather's thing or try to wedge some pieces of metal in place to hold the hex thing tight. Then use an ELECTRIC impact wrench on it, not a monster air wrench. Now, I did the electric part on mine that was virtually impossible to remove. I didn't have the rounded out problem. It took about 30~45 seconds of impact wrench hammering to break it loose but all was well after it came out. I found being able to rest the pumpkin cover on a pice of cardboard on the ground gave me much better control to avoid any damage. Good Luck.

Heck , I was hoping no one else had posted... because my instructions will only work if that bolt is a left hand thread... not worth trying to find that....
I would just weld the nut onto the bolt.. but I try not to assume the availability of welding equipment in my answers...
If you use two nuts on the bolt and put JBWeld on those threads... and tighten the nuts AGAINST each other before they start to set up that might work...

With enough JB weld, anything is possible. ;)

An air impact wrench usually has torque settings so you can 'tone it down' for more gentle jobs. You can also run them at a little lower than normal pressure, like 80 or 70psi to soften them up even further. Just as a hint.

leathermang's method should work fine, but if you are disassembling things anyway, taking the cover off and putting it on the ground would probably make the job easier, just because you've got more room to get a good angle on it.

peace,
sam

I don't know.. if you take it off how are you going to hold it ? This is not a really thick piece of metal... not much way to Evenly hold it without warping it.. I think doing it on the 3rd member if possible is the way to go...

On one of my cars the fill plug had evidence of someone who had used a cold chisel tangent to outer rim to spin it off. If your going to replace it you could try a couple of light raps with a hammer to see if it frees it up. Given that the hex is rounded it may not have been put back very tightly. Back in the 1970's I use to go to a junk yard. There was this old veteran there who swore he could disassemble anything with a well placed chisel and hammer!!

WOW, can't see the forest for the trees
 

How can I be so stupid?!?!?!?! I can remove cover and then remove the fill plug. I become so engrossed in a project that I lose objectivity. As per usual one of the regulars ALWAYS comes through for me. Without this forum and it's wealth of knowledgable members I would be lost and poor. And probrably walking. Thanx to all. :D

"How can I be so stupid?!?!?!?! I can remove cover and then remove the fill plug."

I would try it in place first... once you get it off... if it is really stuck... then you have a problem holding it and applying large amounts of force without bending it...

I'd be tempted to just replace the whole cover, fill plug and all. There are plenty of W123s in my local U-pull-it yards.

When trying to remove the block heater plug (my car didn't come with one..I added it) the bolt/welding/breaker bar meathod got us a lot of twisty bolts :)
Just be careful...you are working with serious torque UNDER a car :)

oh god yes. I put a block heater on a 80 240D that never had one...
After the chisel, it took three guys and an 8ft bar extension under the car to bust it loose. Plugs can be REAL stubborn sometimes.

I did mine from above the car.....I was to darned affraid of dropping the car on me.

Gave me a chance to degrease that side of the block too while I was in there. But it did cost me a set gaskets............

Plan of Attack
 

Cleaned fill plug, will use JB Weld and attach a bolt with 2 nuts, one as a jam nut. If that fails, then I will try the chisel. If that fails, will replace diff cover. Thanx for your help.

Yeah I did this when I had the manifolds off to install my pyro and clean things up. (So from above as well)
Ended up having to use the oxy-acetelyne to heat up the whole mess to even get it to break loose.
I have video of the SD with no exhaust manifolds driving it out to the wash rack :D