LOOKING FOR SEAL REPALCEMENT AT TOP OF PISTON

Excessive oil at the lift ram top seal? Piston seal is gone. No excessive oil at top seal, probably O rings in control valve.

if its a 4 stroke engine then you have piston ring or valve seal or head gasket problem ! compression test 100 psi or more ! remove exhaust and pressure test piston and put some oil in exhaust port on valves with piston at top dead centre and look for bubbles and air leaking past valves , and listen for air passing into crank case which tells you if rings are leaking ( put oil on top of piston to cover the top ring the second time you test this to see if better seal on rings ) !

Check band # 175520 (black rubber band around the outside of the cylinder) is what causes the piston to retract. If the check band is in place, then problem could be caused by cracked lower bumper, worn piston oring or cylinder seal on the headvalve. IF the cylinder seal is bad, air will leak between seal and the top of the cylinder and could push piston down cylinder. If piston oring is too loose, the piston will not stay at the top of the cylinder. If you point the nose of the gun up then down again and the driver moves within the cylinder, replace the oring. Good luck

The Bostitch SX150 pneumatic brad nailer/stapler uses air to both drive the brad or staple and to return the driver/piston assembly to the top of the gun for the next firing. There is no spring that goes into the sleeve or under the piston. If your driver is not returning to the top of the gun you may have put an o-ring or seal in the wrong place or left one out. The o-rings and check seal on the bottom half of the driver sleeve are what control the air that returns the piston to the top so check those first.

Usually there are four things that affect the driver not reaching the top of cylinder. Piston oring too tight or too loose, exhaust air is restricted at top of gun , check valve oring is missing, or air leaking down thru blade seal. Assuming that the piston oring is ok and exhaust is not restricted, make sure that oring # 092235 is in place covering the small holes on the outer lower portion of the cylinder. this is the check valve that causes piston to come up. If, however, too much air leaks down past the blade seal, the driver will not make it to the top. Blade seal is a metal washer with slit just large enough to pass the driver blade. If worn, just make a washer out of tire tube and make a small cut with sharp blade just large enough to pass the driver blade. Make the washer larger than the metal washer and just place it on top of the metal washer. Put back together and nail away. Good luck

Since you've already taken one piston out and got the other one almost out, I'd go ahead and get both out and put new seals in them. Once you get the piston out, you'll probably see why you could not push it back in. It's probably got some corrosion looking stuff we call "shale" on the piston. Now that this mess is between the piston and the seal, it's very tight. Just go ahead and rebuilt the caliper.

Good Luck
Steve

how do you know you need the piston seal. mine also will not build pressure, I think it is the valve assembly that is under the piston. IF you find parts please let me know source. I do not understand why people above posted about the manual. you clearly are not looking for a manual.

Problem sounds like valve plate /reed valves or worn cylinder /vinyl ring. Easy to check, push piston to top position and examine cylinder neer top looking for scratches. If scratched, most likely vinyl piston ring/s are worn and allowing pressure to leak past. If cylinders look good /shiney all the way up to top, remove head/s and examine reed plate/s for missing/broken reeds and or torn gasket/s. If your reed plate is missing one reed and your are good at being creative, you can seal individual hole by threading and plugging with thin piece of bolt. Good luck and good holidays

first you must remove the lever from the master cylinder, then you will see a rubber seal this must be removed, it is not always possible to remove this seal without damage so i would suggest u find a replacment, the outer of the seal can corrode to the master cylinder, once you have removed this you will find a circlip which holds in the piston, remove this keeping a slight pressure on the piston as it is spring loaded, remove carefully so u can ensure correct reassembly of parts, in some occasions the circlip is located on top of the rubber seal.

Many causes for this problem. Some things to check. Push the driver up by hand to see if it moves easily /hard. If hard, check for bent driver or dry cylinder. If it moves easily, check piston oring too worn and /or air could be leaking down past the bumper area. Most guns have very close fitting bumper or a seal below bumper. If too much air leaks down past bumper driver will not return fully. Check seal could be loose or broken. Remove cylinder and look for check seal covering a row of holes on outer/mid to lower part of cylinder. could be a band or oring and should fit rather tight. If ok only other parts to check are the headvalve and piston stop. Piston stop should not have cracks or missing pieces (piston stop slows/stops piston when it returns to top). Head valve should be well lubed. Good luck