If you're not losing fluid, (which shouldn't happen only when turning anyway), raise the front wheels off the ground and check them for loose wheel bearings. I suspect your symptoms would be a little different, but if one is loose, the rotor will wobble and push the piston back into the caliper. The NEXT time you press the brake pedal, it will go down too far since more fluid is needed to push the piston back out.
Also check that both front calipers are mounted solidly and the slide bolts aren't loose or missing. If you can duplicate the problem while the truck is not moving, have a helper press the pedal while you are underneath and watching for movement in one of the calipers.
For the pedal to go further than normal when there's no fluid loss, a caliper piston has to be coming out too far, a rubber flex hose is expanding, or the rear shoes are out of adjustment. A hose or shoe adjustment problem will not be related to turning; it will be there all the time.
Something weird you might consider, if the problem does not occur when the truck is standing still, is to check if your truck has a height-sensing proportioning valve attached to the rear axle. Most trucks and minivans have them to set how much brake fluid pressure goes to the rear wheels compared to the front. That valve is designed to be non-adjustable for passenger cars, but for trucks and minivans there can be such a wide variation in how heavily the rear is loaded. Since we're looking for something unusual, during right turns that valve might let more brake fluid go to the rear brakes, and if they're out of adjustment, that would let the pedal go down too far.
Does this problem occur when turning just a little to the right or do you have to turn fully sharp right? Does the truck have to be moving?
Thursday, July 7th, 2011 AT 8:07 PM