Short answer:
It was the right brake hose.
Long answer:
My wife drives this vehicle. When she told me that it was pulling to one side during braking, I blindly replaced the brake pads on all 4 corners without driving it. The first thing that should have tipped me off that there was a bigger problem was that it was extremely difficult to get the right front caliper piston to retract (so I could get the old pads off).
That alone wouldn’t have isolated the problem, but I could have disconnected the brake hose from the caliper and then seen that the piston could have been depressed easily and that the problem was in the hose. (I'm not sure if this is necessarily true.)
So a couple of weeks later when I actually drove the vehicle, I realized that it was pulling to the left extremely bad and that there was still a problem.
Remembering the problem I had trying to depress the right front caliper and the fact that it was pulling to the left, I first replaced the right front caliper. This did not fix the problem. Another thing that should have tipped me off was that when I removed the hose from the caliper, very little brake fluid dripped out (although I couldn't remember what to expect, so I didn't know if that was normal). After that, I replaced the left caliper (knowing that wasn't going to fix it) and the right brake hose.
When I removed the brake hose from the left front caliper, there was a huge difference in the amount of fluid that dripped from the line compared to the right brake line (a tablespoon compared to a cup). By this time, I was convinced it was the right brake hose.
The following are some things I read, but didn’t turn out to be true in my case.
1) I had read that if the steering wheel turns when the brakes are applied that this is an indication that the problem is the front suspension. Mine did exactly that, but the front end suspension is fine.
2) I had also read that a visual inspection of the brake hose would reveal if that was the problem. Although the hose was my problem, the hose looked fine. When I removed the hose, I couldn't even blow through it with an air compressor, so I sectioned it. All parts of the hose where fine except for the part of the hose that was covered by the mid-line mounting bracket. The bracket had rusted and it looked like the rust had penetrated the hose and clogged the passage. I’m assuming there must be some metal in the hose. It was clogged so hard; I had difficulty driving a nail through the hose in that area.
