You don't have to disconnect the brake line from the caliper unless you are replacing it. Have you pulled the old pads out? They might hang up the whole assembly even if you have removed the two bolts that mount the caliper.

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1981 300TD
2005 C55
2004 E500
1999 ML430
1992 400E
1998 C43
2001 SL500
1988 300SEL
1986 190E 16V
1991 190E 2.6