OK, so I pulled the MC away from the booster. No sort of rubber ring to be found. A-Ha! You guys are the best. There are a couple of grooves on the M/C where it touches the front face of the booster, and then there's the cylinder itself that sticks into the booster. Which location does the o-ring go to? and, who knows what size ring I need? The haynes manual doesn't say, and the steaky site is down . I asked at Autozone, and of course their computer sez "we don't carry that seal..." If this is something I can buy @ a generic place that would be great, since this car is my daily driver. Thanks againg for all your help.