Volvo Repair: Brakes grab on my 1988 740 Turbo, brake hoses, cylinder problem

Question
When the brakes get hot the pedal starts to get real hard to push, then the front brakes start grabbing and eventually almost lock, only allowing the car to go about 10mph. Once the brakes cool, they release and work fine again until hot. Does this sound like a master cylinder problem or calipers?

Answer
possible caliper or bad brake hoses.when they lock if you loosens a bleeder on a caliper that is sticking and fluid comes out under pressure the hoses are collapsing holdin perssure if it just comes out by gravity than the caliper are possibly sticking.