I have a 2003 F250 Super Duty 4x4 with 270,000 miles. I have been having dragging brake problems. I bought some part store rebuilt calipers and they failed shortly after install. I have the original brake calipers for the truck and had them rebuilt last year because brakes where dragging from those part store rebuilds. At that time, I replaced all the rubber hoses, rotors, brake pads, had the calipers cleaned powder coated and rebuilt with new seals and flushed the system with a gallon of brake fluid. Now a year later an about 15,000 miles the front brakes are locking up again. I checked the hoses to see if they had swollen closed, not the problem since good fluid flow both ways, removed the calipers and the pistons where stuck. I finally removed the pistons from the calipers with alot of compressed air and found some build up of crud around the piston under dirt seal but in front of inner seal. The pistons are Phenolic pistons so no rust or corrosion on them. I purchased 2 caliper rebuild kits with the square seal and dust cover not bottom end kits but higher cost kit. I have cleaned the inside of the calipers with a stone hone and there is no dirt, rust or contamination inside, I also sanded the pistons slightly to remove the crud which was stuck to them.
So heres' the dilemma.......... The pistons fit snug with a little clearance in the caliper, (no seal installed) this is normal I'm assuming. When I install the square piston seal in the groove and try to install piston I can not push piston in no matter how much force I use, "I can't get it in". Yes I have is lubed up with brake fluid and even have used some brake system grease to aid in installation of piston. I though maybe bad seal kit (wrong seal)? bought another rebuild kit and same issue, can't get piston in calipers no matter how hard I pushed.
So question ?? How tight is the piston supposed to be in the seal? Should it not be able to be pushed by hand with some effort? (since piston needs to move back to release brakes just by releasing pressure on pistons by relieving brake pedal pressure). I am afraid if I force these pistons into the calipers via c-clamp, they will not work correctly and be back where I started.
I know several out there will say go get some rebuilt calipers from local parts store, I have tried those and I did not have much better luck with them, plus I want to use my stock calipers which came on the truck. I am out of ideas on what to do so I am asking for some help from some experienced brake guys. Thanks for your input and help.

 

I was in the same situation you are in, parts stores lasted a year or two then seized up, I have found that doing the seal kit and new pistons was the best way, cost is usually under $50 a set for 4 pistons and seal kits. You have to make sure both the seal bore and the dust boot bore have zero rust/scale in them, the pistons will be tight and need a c-clamp to push in, make sure it’s square so it doesn’t chew up the seal or the piston against the calliper bore. The seal is designed to pull the piston back just enough to relieve pressure on the brakes and not cause them to drag(the hydraulic system may help with this also).

Make sure everything is surgically clean, I wouldn’t reuse pistons, brake fluid the seal and piston side for install and use a c-clamp to gently push them in and you should be good to go.

 

Thanks for the advise, where did you purchase your new pistons? were they Phenolic like OEM? Also what brand caliper rebuild kit did you use? You wouldn't happen to have a link for these parts. Thanks again for your help.

 

They are phenolic pistons, I get them from rockauto

 

thank you, rock auto is where I purchased the Carlson caliper seal kit and like your truck the pistons are out of stock with no date of availability.