Are you sure the left front caliper is sliding freely on the spindle and the slide pins? Drive it a bit and stop some where and see if the left front wheel is hotter than the right. If it isn't then I would say alignment, How are the tires wearing? And have you checked the BJ's? Also maybe the bushings in the suspension arms.

 

one of the valves is going bad. porportioning valve is my bet.

a brake system is a hydraulic system. before throwing parts at it (like these others have suggested) its best to diagnose the problem.

You said it was pulling to the left. #1 cause is a sticking caliper. you already replaced that. it wont matter to replace them in pairs, because its a hydraulic system. a new caliper wont "bite" any different, as long as the pressure is the same going to both.

your still pulling to the left, so a passenger caliper wouldnt solve that problem. your not having the same amount of fluid on the left side as the right side. so that points to a valve.

good luck.

 

The only reason it will pull to the left (While he's driving and not on the brakes) is if the caliper is stuck on the slides or where it slides on the spindle are froze up.(or a suspension or alignment prob) It has nothing to do with the proportioning valve while you are driving.

 

The calipers both came with new bolts and slides, and I checked them b4 I put them in. I remember reading on here that improperly adjusted camber or caster (don't remember which) causes pulling. I assume that this can cause pulling even more when braking?

 

did you check you wheel bearings and/or hub? did you break-in the pads properly?