Originally Posted by ScotcH
Why the hell would you drain the block to change the thermostat? What a waste of time. The sealing ring might cause leaks since it's a crush ring, and it will not reseal right. Keep an eye on that spot. I would replace it when you get a chance.
Also, in the future, use the proper spot for jacking. You can put the jack stands on the frame rail behind the LCAB lollypops.
Maybe he was doing a coolant change and t-stat replacement. as for the crush ring, I've done it about 3 times with out changing them and they haven't leaked on me. This was on a E30, E36 and E28. werid.