WPG -
When you get rebuilt calipers, look at the surfaces to see if they have many corrosion pits. We are getting to the point where calipers can have several lives and long exposure to the elements.
When cleaning calipers for a rebuild, the one thing that rebuilders can't do is resurface the dust boot groove, so it is left with whatever pits from corrosion existed, and that inhibits the new dust boots from sealing as well as when the caliper body is new. You can pack that area with silicone grease, although when in that situation, I caulk the boot/caliper body connection with electric RTV. That version of RTV is not cured by acetic acid, so it doesn't promote corrosion.
A long post that I did on FTE long ago.
6.0L Power Stroke Diesel - Brake caliper issues - Does anyone know a company that makes replacement brake calipers for 99-04 trucks/00-05 Excursions that dont start dragging within a couple years? I replaced the fronts (not sure if original caliper) in Feb 2015 due to driver side dragging BADLY...
www.ford-trucks.com