Rear D Fill Plug Holy S**t
 

OK, so I've had the car up on the ramps twice now, trying to knock the fill plug off so I can change the rear differential oil. I didn't think it would be so ridiculously difficult. I've emptied almost an entire can of Liquid Wrench on it trying to loosen it up. It's rusted to hell. I think the last time it was taken off was at least 10 years ago (random guess). I'm using a 1/2 inch driver and 14mm hex bit attached. It is a swivel type so I can get some decent angles on it....still, after pushing, pulling, hammering with all my might, NADA. I've dealt with some tough plugs in my life but nothing like this.

I'm not Arnold Swar_______er, but I'm not slim pickens, either. I probably have as much muscle mass as your average German, though I'm not German. In other words, Mercedes should've/probably expected a dude with my strength to be working on this thing. Of course not on a plug that's been there for years without any love. I just bought the car a year ago and am doing all the maintenance to get it up to snuff. This is the last thing on the list.......krikey.

Any advice beyond "just keep doing what you're doing" is appreciated. I understand if there's nothing to say....hm. Is it possible it's never coming out?!?!?!?!

Thanks guys.

Get access to an air-powered wrench, and it will come off quite easily. Perhaps a visit to a local mechanic with a plate of brownies is all it will take...

Cheater bar.

Get a piece of tube over the end of your ratchet and push/pull on it.

JBG,

I did this. It's tough.

It took me an 18" breaker bar extended with about a footlong section of pipe to get enough leverage to break it free. Heating the plug with a torch will also help the situation, but I did not need to go this far. With your rust it sounds like you may need to go there. If you dont have a torch theyre cheap at the local hardware store.

When you put it back, needless to say, put some anti-seize compound in case you ever are in the area again.

Good luck,

dd

Take a high-speed run on the highway, what will get it nice and hot too.

A cheater bar got mine out. I found it didn't have a copper washer. Maybe some heat would help, too. Steve

Air impact gun.

I did this not too long ago, I ended up using the handle off of my floor jack as a cheater bar--about four feet. It still took some major force and a few choice words were thrown in for good measure. I had soaked it for over a week with PB Blaster everyday. I was going to use my impact wrench but I was afraid it might strip the plug and then I would have been in a real mess--prefer to use old fashioned force on things that would be a major PIA if the impact wrench tore them up. Get a bigger pipe and keep trying it will break free--just wait until you see what comes out. Good luck.

CAREFUL WITH THE IMPACT. I think the situation you are running into is similar to mine on an old Muncie trans. I when to change the diff lube in it as well and the steel plug had pretty much welded itself into the aluminum case. I tried everything, which led me to the impact. 30 seconds of impacting and boom, sheared the plug hex right off. Had to drop the trans disassemble it drill it out helicoil it, not fun you get the picture.

Heat the housing surrounding it gently, and wick some wax into the threads. Your children should be able to move it then.

These plugs are often tapered pipe plugs and have no aluminum washer. I always take my 14mm Allen wrench I bought for this purpose in 1976, and a heavy headed hammer, and bang on it. Hard. Clean out the hex socket, and to get a really good grip between the wrench and the socket, wet the end of the Allen wrench, and then dip it in Ajax or Comet. I read that little gem here a while back. It keeps the wrench in the socket better, but you have to clean the socket out good.

Once it moves, you will have to keep knocking on it until it really gets "hand tight" and you can turn it by hand. When I put them back in, I make sure the threads on both parts are clean, then I run it in by hand and tap it shut with a few easy hammer blows. It snugs up and stops turning, which is when you stop tapping with the hammer.

I give the ones with the aluminum washers and the straight threads a similar treatment to remove them, but when you put them back in, I believe there is a torque value specified. If you don't have a torque wrench, red face tight works from experience. Jim

36" breaker for me, No problem. Pop the fill plug first if you can use a fluid evaccuator and the refill what you took out.

I'm surprised no one posted the easiest way to do it:

1. Put car up on small ramps so you can get under it.

2. Insert the drain plug socket with an 18"+ breaker bar on it in the right position so that:

3. Insert floor jack under handle of breaker bar so that when you begin lifting, it will force the plug counter clockwise.

4. Keep going even when it seems it will lift the car off the ramps, it will "POP!" free.

This has worked on all 3 of our MB's that I have worked on. On mine it raised the car a good 8-10 inches on the suspension before there was enough force to break it loose.

Heating the diff around the plug should help too...expands the metal.

Good luck!

Oh !@#$ Now i remember i had to do that as well. Absolutely right!!!! Be ready to barf when that thing comes out cause the diff oil has a smell like no other EWWWWW. Wear long rubber gloves..

Yep. it smells just like the engine oil that get trapped inside some threaded recess in the block. Since it is rotted dino's, makes sense that is smells like roadkill on a hot summer day...