I have "gravity bled" the brakes before and although it works, it's not the best way. I hate to pump the brakes and the hazzard of overextending the piston can be problematic on old calipers. I think there is more chance of leaving air in the system.

I bought an EZ-bleed and changed the brake fluid in my SL so fast, I hardly knew I started. It is about $30 and saves a lot of time. It's well worth the money. (My $0.02).

Steve
'85 500SL Euro