850 R rear brakes
 

Send them back to FCP and get them warrantied.

if the caliper sticks, it'll eat up the pad. Always a good idea to let some fluid run through when changing the calipers and consider doing fluid change. Calipers fail when either the rubber boots get debris in them or tear and let dirt get in or the brake fluid is old and there's moisture which can corrode the cylinder walls. New calipers deserve new fluid :-)

Brake fluid absorbs moisture so the whole system should be completely flushed every few years. Replacing rusted calipers w/o flushing the system is just inviting a repeat of the same problem. If the brake fluid in the reservoir is dark in color, it needs a flush. Easy to do with a pressure bleeder.

BTW: rebuilding calipers yourself isn't that difficult, especially if you have access to compressed air. A seal kit is much less than rebuilt calipers. As long as the pistons aren't pitted from rust, and they usually aren't.

Use a friend to power bleed. Plenty of power available but you really have to have somebody in the seat.

I don't know about you guys, but I find that the rear pads themselves are way too tight on every Volvo I have worked on. I don't feel super-comfortable that the pads themselves don't stick and get hot, damaging the caliper. I have more and more cars with this problem now, due to trends in brake design, but that is another subject. I'll never forget replacing brakes on Liz Webster's Volvo wagon in 1987 and the pads wouldn't really go into the caliper in a friendly way. They haven't really ever fixed that.