Es wird von oben geschlagen. Hier jetzt mal mit Bildern an einem E32 750, dem hab ich naemlich auch geholfen, kopiert:
Solution to remove a stuck crossmember when changing the upper oil pan gasket
I've changed the upper oil pan gasket on my 1991 750i, now I'm doing it again on my new 1989 750iL Highline. I don't know how much BMW would charge to do this job, I'm sure a lot. They do it by the book, remove trans, hoist the engine, bla, bla.
Shogun and others have already provided wonderful info on the forum how to drill holes in the upper oil pan to be able reach the hidden 4 bolts thus being able to get the upper pan out forward.
I personaly like to NOT raise the engine, I don't have to remove anything up top, I just raise the engine 2-3mm and support it, using a piece of paper as a measure touching the top of the fan, I can see how the engine is moving.
Once the bolts are out of the front crossmember (leave two in loosely), it always still is stuck, the right hand side pin-dowl on the crossmember is stuck in the cars frame. Won't come loose on it's own or with sweat, foul words or beer.
I've added a few photos how and where to hit the crossmember VERY hard from straight above and very near the dowl which is stuck. You need a wooden broom stick cut to appropiate lenght, and stand it straight down vertically and parallell to the oil dip stick tube, just rear of it. Take a cloth or a spung and squeeze that in between the manifold and the washer fluid tank. This will guide the broom stick so it remains standing up straight.
Now, take a huge wooden log, or something else VERY heavy and big enough, it hard to miss. A sledge hammer does not have enough mass or force. Swing the log from above straight down and hit the broom stick. A few really hard hit and the pin dowl will finally let go. TaDA....
Have a beer, then drill your holes in the Upper pan.
Photos:
da ansetzen
2014-12-09223131_zps387724e7.jpg Photo by fritzenos | Photobucket
2014-12-09223148_zps443e1fb0.jpg Photo by fritzenos | Photobucket
2014-12-09223315_zps69b31a40.jpg Photo by fritzenos | Photobucket
2014-12-09223113_zpsff0f325f.jpg Photo by fritzenos | Photobucket
2014-12-10003501_zps7b6042e4.jpg Photo by fritzenos | Photobucket
I also used the weight of the engine and a floor jack, moved up and down a few milimeters, loosend the bolts two turns.