[Gasoline Fumes]

My parents' 1991 Toyota Corolla wagon has a weird brake issue. Before driving the car, the front wheels spin just fine. After driving the car, the front wheels are very difficult to turn and the wheels are hot. Driver's side is hotter and harder to turn. Calipers do not stick after pumping the brake when cold.

What's causing this? Brake hoses? Master cylinder? Calipers appear to be in great shape and at least the driver's side is not seized. I didn't inspect the passenger's side caliper very well since it's less of a problem. Both calipers were replaced with rebuilt calipers a few years ago.