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How to Replace an O Ring on a D51256 Nailer

When an o-ring goes bad on your DeWALT D51256 Nailer, it can render your nail gun useless. Air leaks in the D51256 reduce the pressure in the cylinder. This causes the piston driver to hit the nail with less force and possibly fail to drive the nail through the material. These weak hits can result in having to repeatedly remove finish nails throughout the job. If an o-ring needs replacement, it is best to use an o-ring kit and replace them all. This will ensure that you will not have to replace an o-ring your D51256 Nailer again in the near future.

Things You'll Need

DeWALT o-ring kit, part number: 623236-00
Allen wrench, 4 mm
Safety glasses

Instructions

- 1
  Put on the safety glasses. Open the o-ring kit. Separate each o-ring by size. You will need to compare these o-rings to the ones you will be replacing.
- 2
  Unhook any air hoses from the nailer. Unscrew the bolt at the back of the nailer using the 4 mm Allen wrench. Remove the busing. Replace the o-ring on the bushing. Remove the black deflector. Replace the o-ring under the deflector.
- 3
  Unscrew the 4 bolts around the yellow cap with the 4 mm wrench. Remove the cap. Remove the black gasket. Inspect the gasket for any damage or dirt.
- 4
  Remove the hold down cage. Remove the seal. Remove the cylinder. Replace the o-rings on the cage and cylinder. There could be three to five depending on the year your nailer was made.
- 5
  Remove the cap and spring. Remove the valve. Replace the three o-rings on the valve.
- 6
  Remove the piston driver assembly. Replace the o-ring on the assembly.
- 7
  Reassemble the nailer in reverse order.

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