Rear differential drain plug damaged 87 300 SDL
 

So after I got done flushing out my coolant and filling her up with the MB coolant. I thought it would be a good time to swap out that nasty old rear differential oil. So I jack the car up, and get the filler plug off, first. Not a problem. And then I go and look at the drain plug and it seems to be smashed/ chewed up, and just not in a good mood. Someone, before me, didn't treat her nicely.

I attempted to get a rubber hammer and ask it nicely to go into the plug, but that didn't work out so great. So I'm back to the beginning. I was able to get my finger into the differential to see how bad the oil was. DON'T EVER DO THAT!!! I'm going to have to cut off my finger to get the bunt smell off and it was bubbly/ foaming. Not good.

So anyone have any idea how I might get that out of the rear differential. And where I could order another plug? I attempted to find one on the forum parts shop but couldn't find it. I'm hoping not to go to the stealership for it.

Some options
 

If all you want to do is change the rear differential oil you could leave the drain plug where it is and suck the old oil out. The tool for doing this used to be some where in the $13-$20 range. See picture.
You can get one at the local parts store.
Another option is to leave the plug in and loosen or remove the differential cover, drain, and reinstall it with a gasket or sealant.
Go to the junk yard and get another differential cover with a decent plug (remove the plug at the junk yard to be sure it will come out).
Otherwise you will have to do what ever is necessary to get some sort of Eze-out out into the plug to turn it out. Usually requires the proper size drill, Eze-out and sometime a tap to restore the threads.
They may have a newer type of EZE-OUT now for stripped internal allen/hex type slots that you will not have to do any drilling to use but I have not seen them or have any experience with them.
Another messy option would be to drill, tap, and thread the existing plug for a smaller american pipe plug. When the drill enters the differential the draining oil will was out the chips. When you use the tap put thick grease on in the tap flutes (grooves) and the grease will trap the cuttings as you thread the tap in.
Motor Drain Oil Fluid Suction Siphon Pump

http://i242.photobucket.com/albums/f...el911/pump.jpg

I think Diesel911 has you covered with correct options. You can remove cover and let that god-awful smelling mess drain and reinstall cover. Should be fine that way, or as stated go find a cover at a salvage yard.
Man that stuff always smells nasty! :eek:

You probably should remove the cover to see if any metal particles from the old plug got loose in there :rolleyes:

BTW, one should always remove the fill plug first, before the drain plug just in case it (the fill plug) is stuck.
Anyhow you will need to either find a junkyard w/ a 126 chassis to snag a p;lug from or buy one from the dealer, it can't be THAT expensive.

I haven't seen those plugs sold as aftermarket or replacement items. When you remove the cover let it drain a day (or longer) to get all the stinky stuff out. Some purists have said they flush the old goop out by running synthetic 75W90 in there and replacing it after a few months with more fresh lube.
I recommend Amsoil synthetic for its longevity.
The level isn't that critical. I've never measured it out, if the car is level you just fill it until it spills out of the fill opening. I usually have access to a lift but if it was jacked up I'd still fill it by eyeball, let the car down with the fill plug out to let it drain a bit then jack it back up and replace the plug.
Good thing you don't have a 124 chassis, the rear cover is sandwiched against a lower cross member and its a big job to get to the cover.

I'd remove the cover, clean it up and torch that plug out. I can't imagin the dealer can't get it the next day for a few bucks.

I used Mobil 1 75w90, but I use Mobil synthetic fluids throughout the whole car. Amsoild or Redline work.

Unless there's something wrong with the rear differential, there shouldn't be a reason to change it, depending on how many miles are on it. My last MB had it's original in it when I sold it @ 16 years, with over 305K on it. No sweat, checked it often and it was always clean & fine.

What's up with the damaged plug, anyway?

I'll check some junk yards in my area. for a new plug. I'm not sure whats up with the plug, I think someone used a 13 mm and damaged the plug. The 14 mm Hex doesn't want to go all the way into the plug.

Tuff times.

I believe he said the wrench area of the plug was stripped out; no tourch will help that unless you mean burn the plug out with a cutting tourch. If that is the case he possibly would need a tap to restor the threads.

That's exactly what he meant.

The blow torch gets things moving quickly........sometimes the only way to remove a main-fuel filter bolt is to give it a few passes with a blow torch.
Works wonders in thermal surface differences. It'll give it up quickly when hot, believe me!

What are the miles on this car, OP??

No its a big plug, you can do many things to get it out. Torching the cover will expand it and make the plug very easy to extract. You can either tap it with a left hand thread bolt, or use one of those screw extracters.

Read last three previous posts.......

You only want to "heat it up," to make removing it easier.

My personal choice of all the posts I have seen so far and the fact that the differential oil seldom needs to be changed would be to suck out the old oil through the filler hole.
If something else came up later like changing an Axle I would deal with the stuck plug.

This is what I remember reading from the start of the thread:
"And then I go and look at the drain plug and it seems to be smashed/ chewed up, and just not in a good mood. Someone, before me, didn't treat her nicely".
This gave me the impression that there is nothing left to get a wrench on to turn the plug out. To me this means heating the plug will do you no good if there is nothing left to turn it.

As I recall, the drain plug is, in effect, a large Allen-head pipe thread set screw. If the hex recess is damaged, there's nothing to grab onto, with one small possible exception. If enough of the plug is protruding, you might be able to use a hammer and chisel around the edges to gradually work the plug around and eventually out. Gentle warming with a torch beforehand will help.

If that doesn't work, you can suck out the old oil, replace it with new, and leave the hard part for some other day. On that "other day," you remove the cover, drill a hole in the plug, and use an EZ-out to remove the plug. Put rags inside the diff during the drilling to minimize chip scattering and flush well before refitting the cover and adding new fluid.

Jeremy

If you are hell bent on removing the drain plug, buy a replacement drain plug first. Then unbolt the cover and remove the entire cover.

You can then try the heat process that someone suggested. If that doesn't work go to plan B below.

Drill a hole through the center of the drain plug, that metal should be pretty soft, no reason to have heat treated metal for that plug. Run a bolt/nut through it, tighten up the assembly and use the bolt to unscrew the entire plug. Apply anti-seize and install new plug.

If you are lazy and not obsessive (like me) buy that spiphon pump that Diesel911 suggested. That is the easiest. You can pump the old fluid out and then change it again in another month or so. That ought to be sufficient.