brick8

I tried to change the oil on my 1994 100CSQ yesterday and failed. I have been changing my own oil on various vehicles for over 25 years and have never had so much trouble. After removing the plastic engine bottom cover (is this thing really necessary?), I tried for about an hour to remove the oil drain plug without success. I used a 17mm combination wrench, then moved to a 17mm socket with a 2 foot breaker bar and then even tried my compressed air wrench, all without success. The oil was last changed by the mechanic who changed my timing belt,etc. Has anyone else here had this problem? I don't know if it is a matter of it being baked on or severely overtightened. To add insult to injury it then took me a good fifteen minutes to put the stupid bottom cover back on (done just before guests started arriving for dinner). Anyone else here had this experience? I always change my own oil because I don't trust others to use the right stuff, etc.

Barty

That belly pan is a major headache but I keep it on nonetheless. I switched to synthetic oil so I really need to mess with it every 10k miles.
I notices that the plug really tightens with time. That is why it is important not to overtighten it. Your mechanic must have really put an arm to it. The only suggestion I have is to try again with the car warmed up. Let's hope that the different expansion coefficients of the metals (bolt - steel, oil pan - aluminum) will loosen-up the plug a bit. I always use a box wrench. On the positive note, this is one hell of a plug so I would think it would take quite a punding before it would shear so I would not worry about putting some torque to it as long as you have a good quality wrench so you do not strip it. Once you strip it you will be done for sure.

quattro2turbo

Just don't put too much torque or your break the aluminum right off.. Like I did!

moribundman

In many new cars, including Mercedes models, this is the only way, as there may not even be a drain bolt. Just get an oil extractor pump. That's what I would do if the drain bolt were stuck for good. Did your mechanic use a copper or aluminum drain plug washer, or did he not use any? The bolt really doesn't have to be tightened a whole lot, just enough for the washer to make a good seal.

The belly pan is easy to put back on. I assume you are on you back under the car, feet sticking out front: First, guide the front edge under the bumper lip (?). Then fit the left and right rear corners of the pan behind the fender liner. if you do that, then you can easily twist in the rear center fastener, which will hold the whole contraption. You can then install the remaining fasteners without any acrobatics.

brick8

I got it back on ok, but it was a pita, especially with the wife on my case about working on the car on Easter when her parents were about to come over for dinner... Anyway, I took it to the mechanic that replaced the oil the last time and I will let him deal with it.

islingtonaudi

Sometimes I wonder if some shops use an air wrench under every circumstance. Cracked alloys anyone?

quattro2turbo

abrasions and scratches around the lugs but no cracks..

4AudiQ

Mance reported on that several years back.