All Springer/NP/PCP Air Gun Discussion General > Vintage Air Gun Gate

Crosman 1400 weird air leak

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I agree you need the right quad seal.  Also, check to make sure inside your valve chamber where the little white check valve plug goes is spotless.  If you get crud embedded in the nylon plug, it can foil the seal on the check valve and randomly leak or stick open.  Scrub out the valve with some twisted 4-0 steel wool and clean, clean, clean.  Inspect and replace the white plug if necessary.  I think the spring is about 1.25 inches and may be weak?  When you pump the 140/1400, any crud in the pump tube, has no where to go except the little intake hole on the flathead of the valve, thus getting mashed in the white check valve, so clean out that pump cylinder tube really well too before installing the pump rod.
tip:  until I have a 140/1400 running smoothly, I used a cut off nail the same diameter as the pump linkage roll pin, and slide a small o-ring over the end.  Lots easier to repeat a disassembly without having to pound out that roll pin repeatedly!
Hope that helps.

 You can polish the seat for the white check valve by using a standard pencil eraser to dislodge any crust or flakes of funk. Simply stick it down in there and give it the old twist action.
  Polish the pin that transits through by the piece held by the breech screw and holds the valve cap closed against the valve.
  Polish the angled rear surface of the hammer that engages the sear, and the cylindrical portion as well. VERY CAREFULLY inspect your trigger sear for any obvious rough spots and address if comfortable doing so.
  I do not lube the hammer and associated parts that hold and seal the valve cap with anything but pellgun oil/ secret sauce/ ATF etc...

  This may free up the parts and allow your valve cap to seat on the first pump with a click like intended.

Tack Driver 10:
These are what I use in the Crosman blow off valves.

They also have them in Viton 75 duro.

When you put the gun together The thick round disk with the hole in it that the breech screw goes into the screw hole is not symmetrical in the disk, the disk has to face a certain way. Your quad seal is probably fine, I just use an o-ring. A problem area for leaks in these guns is the inside of the tube where the valve o-ring contacts the tube, moisture builds up there, and can pitt the inside of the tube causing various amounts of leakage depending on the amount of pitting.


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