Where are the block drain plugs?
 

Started to change my coolant today on the 560SL and didn't get too far. I can't figure out which bolt(s) are for the block drains. On the passenger side I thought at first that it was bolt #3, but it is not only not accessible, but there isn't a similar one on the driver's side. Then I figured that maybe it was bolt #1, but I removed it and it is covered in engine oil and no coolant came out, so obviously that's not it either. That leads me to bolt number 2. It takes an allen socket and there is a similar one on the driver's side. Is that it or am I looking in the wrong place? The manual says it is just forward of the engine mount and that's where I am I think.

Thanks.

It's the allen head on both sides. This plug also has an aluminum seal ring under it. Be sure to replace the ring and its easy to cross thread the plug sometimes. Don't take an antifreeze bath!

Thanks Shooter. I was wondering about the sealing ring. Don't have any new ones on hand unless they are the same size as other applications that I might have on hand. Do you know the size off hand? I see the World Pac guys have a 12 x 18 x 1.5 listed, but they don't give the application. I'm expecting a bit of a bath. That's why I'm doing it cold.

Okay, here's an update. In both photos, it is bolt #2 that is the block drain as Shooter said. It takes a 6mm allen socket. Each bolt also has a sealing ring that needs to be replaced. The sealing ring is part #007603-014104. It looks to be about a 16 x 20 x 2 aluminum ring, if I'm measuring it right.

I was able to break the one on the driver's side free and a lot of coolant came out. The one on the passenger side won't come out. It looks like someone had a go at it at some point and rounded off the edges so that my 6mm allen socket just turns in the head of the bolt. If anyone has a recommendation on how to get it out, I'd like to hear it. My thought now is to just leave it be and flush the system a few times. I was able to get about 2.5 gallons drained. The system holds about 3.5 gallons, so a couple of flushes ought to get most of the old green stuff out.