I did have the bleeder open when pushing it in ... the piston is out quite far. The pads weren't totally wiped out but were pretty thin. IIRC the last time I did it they were hard to get "started" but once they started moving, it got easier. I'll try again tomorrow with a larger C-clamp ... even with the pad the one I'm using kind of ends up at a funny angle. Even if I can get it moving though, I'd still be worried about how stubborn it was.
I'll go back and study the process of removing and cleaning the piston ... last time I considered it it looked like more than I could handle. It's just one of those things I don't want to do wrong and find out the hard way. I'd rather experiment with one that's going on a car I drive less frequently and vigorously.

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)