1990 wagon with who knows how many miles (the odometer broke years ago). Belongs to a friend.

1. The coolant gauge showed it was running cold once the weather turned cold. I thought it meant a thermostat stuck open so I replaced it, along with the coolant; it didn't change anything. What gives? Anyone?

2. The brakes were a little weak so I thought I'd bleed them since the rotors and pads were good. The left rear caliper only dripped when I opened it; same with the upper bleeds of both front calipers. The right rear and all 4 of the lower front bleeds worked properly. No idea when these calipers were last rebuilt or replaced so I don't know if this is a caliper problem or is it the distribution valve? Any ideas?