I’ve owned a .25 cal Impact since 2015. I have become very familiar with pcp airguns and how to maintain them. This particular example seems to need all orings replaced about yearly. I am not running abnormally high reg preasures (143.4 bar seems to be the sweet spot for this particular gun when firing the JSB King 33.95 Exact King Heavy Diablo mark 1). I have had to replace orings often enough that I recently purchased one of the high end Wika gauges (DG-10) so that I could do the whole oring replacement job and get things dialed back in quicker. AoA did the first and second rebuilds then I started doing them and just finished the 4th two weeks ago. Even when the gun was new and after the AoA rebuilds the gun would leak down from 250 bar to 50 bar in about a month. This is still the case today. I also have an FX Revolution that holds pressure indefinitely. So the leak down of the Impact is concerning but maybe not unusual given the vast number of orings in play. What are others seeing for this gun?
Normal or “acceptable” leak down for FX Impact
- Thread starter 3at32off
- Start date
Zero leak down.
All the o-rings do not fail at the same time and there is no reason to replace them all at once. You test for a leak and fix it. That will usually be 1 o-ring and there will be a reason it failed like a nick or something out of spec. Soapy water will find the problem.
All the o-rings do not fail at the same time and there is no reason to replace them all at once. You test for a leak and fix it. That will usually be 1 o-ring and there will be a reason it failed like a nick or something out of spec. Soapy water will find the problem.
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Having more O-rings certainly increases the probability that a leak will occur, but at the same time it doesn't mean that a persistent slow leak is acceptable or inevitable.
In my experience, a gun that has a slow leak (or that is prone to develop a slow leak within a short time of being resealed) will have one particular trouble spot that just has to be bulldogged until it's pinpointed. If the leak is slow enough or buried deep inside (e.g. valve poppet), sometimes you just have to bite the bullet and strip it down to the pressure vessel and breech (remove stock, barrel, trigger group, etc.) and dunk it under water. Even a very slow leak will soon show a small bubble forming.
That's my last resort of course. If it's a faster leak, painting around the suspect areas with soapy water may reveal the source.
On occasion I've had a very slow leak produce an audible popping sound and that was really convenient
That symptom may occur when the O-ring is extruding into the gap...caused either by sloppy tolerances or an O-ring that is too soft.
It should not be necessary to replace O-rings annually. Certainly not static seals. Those exposed to abrasion (bolt O-rings/breech O-rings) are a different story.
The wrong kind of O-ring may lose pressure by way of permeability but that's not something one would generally run into on PCPs. Good old Buna-N is cheap and reliable with high pressure air.
In my experience, a gun that has a slow leak (or that is prone to develop a slow leak within a short time of being resealed) will have one particular trouble spot that just has to be bulldogged until it's pinpointed. If the leak is slow enough or buried deep inside (e.g. valve poppet), sometimes you just have to bite the bullet and strip it down to the pressure vessel and breech (remove stock, barrel, trigger group, etc.) and dunk it under water. Even a very slow leak will soon show a small bubble forming.
That's my last resort of course. If it's a faster leak, painting around the suspect areas with soapy water may reveal the source.
On occasion I've had a very slow leak produce an audible popping sound and that was really convenient
That symptom may occur when the O-ring is extruding into the gap...caused either by sloppy tolerances or an O-ring that is too soft.It should not be necessary to replace O-rings annually. Certainly not static seals. Those exposed to abrasion (bolt O-rings/breech O-rings) are a different story.
The wrong kind of O-ring may lose pressure by way of permeability but that's not something one would generally run into on PCPs. Good old Buna-N is cheap and reliable with high pressure air.
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A good mechanic will always diagnose the problem and then fix it.
A "shade tree" mechanic throws parts at it and hopes that works.
A "shade tree" mechanic throws parts at it and hopes that works.
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Only thing i can add is my 2017 .25 Impact has had 0 leaks. I have adjusted the (huma) reg many times. Ive probably run 4000-5000 pellets through it maybe more as ive lost track.I wash and lube my pellets and rarely need to clean the barrel,might be why the breech orings lasted so long
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https://youtu.be/bSscQBR6hWA
Have a look at this video by Ernest and see if you can isolate the problem.
If not it would be worth sending it to him.
Have a look at this video by Ernest and see if you can isolate the problem.
If not it would be worth sending it to him.
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I have a Gamo Coyote that had a leck that i fixed a few time's.By accident i over filled it by 3 or 4 oo psi and that must had sealed the leak,holds for ever now"Willy
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Thanks for the replies. I have watched all the videos mentioned. (That is how I got familiar enough with the disassembly to start doing it myself.)
The reason I replace all the o-rings is because if I am going to take the whole gun down there is no good reason to leave a year old (or older) o-ring in it. Like all plastics and rubber products, o-rings out gas and loose their plasticizer over time becoming more brittle. For the 5 cents (or less) cost of each o-ring the cost is insignificant compared to the time. In a former life I worked on high end presses (Heidelberg) for a living. If you have one of those apart, you replace every o-ring, bushing, bearing and many wear points while it’s apart.
I agree that static seals should last for years and likely would be fine if I left them in the gun. Two of the rebuilds were precipitated by the X ring that seals the valve rod at the end of the valve tube (B23 - 19768 in the exploded diagrams from FX). In the newer guns the valve tube has been redesigned and the x-ring is now a thicker and more wear resistant urethane o-ring. This is a seal that is not directly observable when the gun is assembled far enough to put it under pressure. As a result, I upgraded the gun to the new design last month in hopes that would eliminate the issue... not so far.
Leak detection sprays and soapy water have never formed a discernable bubble on those areas that are accessible. I haven’t dunked the gun underwater yet but that is the next thing now that I know some people have zero leak down. Need to take all the steal parts out if it first.
More diagnosis is necessary to find it. Hope it isn’t something that is machined improperly as later guns seem to have benefitted from lessons learned from the early guns.
The reason I replace all the o-rings is because if I am going to take the whole gun down there is no good reason to leave a year old (or older) o-ring in it. Like all plastics and rubber products, o-rings out gas and loose their plasticizer over time becoming more brittle. For the 5 cents (or less) cost of each o-ring the cost is insignificant compared to the time. In a former life I worked on high end presses (Heidelberg) for a living. If you have one of those apart, you replace every o-ring, bushing, bearing and many wear points while it’s apart.
I agree that static seals should last for years and likely would be fine if I left them in the gun. Two of the rebuilds were precipitated by the X ring that seals the valve rod at the end of the valve tube (B23 - 19768 in the exploded diagrams from FX). In the newer guns the valve tube has been redesigned and the x-ring is now a thicker and more wear resistant urethane o-ring. This is a seal that is not directly observable when the gun is assembled far enough to put it under pressure. As a result, I upgraded the gun to the new design last month in hopes that would eliminate the issue... not so far.
Leak detection sprays and soapy water have never formed a discernable bubble on those areas that are accessible. I haven’t dunked the gun underwater yet but that is the next thing now that I know some people have zero leak down. Need to take all the steal parts out if it first.
More diagnosis is necessary to find it. Hope it isn’t something that is machined improperly as later guns seem to have benefitted from lessons learned from the early guns.
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I've got two Impact Xs and each one showed a very slow leak at one time. I snugged the guage for the main tank, but that wasn't it. I then found it at the steel/rubber washer on the trigger block side of the fitting that the tank screws onto in each case. Just a little snugging of the fitting into the trigger block was all it took. Keeping an extra couple of those steel/rubber washers on hand like O-rings is a good idea. For what it's worth, the leak test spray (or soapy water) took some time to show the start of bubbles.
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Acceptable leakage from an Impact is Zero. I've had leaks, but the gun is capable of holding air for just about ever. I personally did the rebuild and now, zero leakage. The leak spray helps, but isn't infallible. It does take time and some of the places where it leaks can be really hard to detect.
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Take the barrel off and fill the rear block transfer port with leak detector/soapy water to check the valve.
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I use a strong solution of dawn dish soap towel and air dry them then i use Napier power pellet lube...Just a mist from the spray bottle in a zip lock bag, roll them around a bit then into the tin they go.
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I had a QB one time that had a SLOOOOOOW leak. Turns out it was the poppet seal. (I had replaced original with a peek one) This is just what I did. Removed barrel and I filled the valve with leak detector and then watched it with a 10x loupe. VERY tiny bubble would come up to the surface every few seconds. Couldn't see it with the naked eye.
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Did you lap the poppet against the seat to get it to seal better or did you move to delrin?
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Well, I had something similar with my FX Impact and inmediately took it to Manolo who is an excelletn airgunsmith here in PR and well known in the airgun competition circuit.
He knows this rifles from inside out! His reputation has reach within the serious air gun competitors in the USA who mail his guns to get them fix.
I rather to take him to geti it fix and avoid the head ache. FX Impacts are not unbreakable air guns they have plenty of falls. I am very lucky to have a Professional airgunsmith to were I take my airgun and be fix correctly avoiding headaches.
He knows this rifles from inside out! His reputation has reach within the serious air gun competitors in the USA who mail his guns to get them fix.
I rather to take him to geti it fix and avoid the head ache. FX Impacts are not unbreakable air guns they have plenty of falls. I am very lucky to have a Professional airgunsmith to were I take my airgun and be fix correctly avoiding headaches.
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Solved:
Had to submerge the gun (with everything I could removed) and after 30 minutes a bubble did form at the edge of the high pressure gauge right where the glass crystal and the chrome housing meet. Given the position of this leak, it is no wonder that it was not caught by any previous technician or servicing. New Wika gauge installed and after three days, no change in pressure.
Had to submerge the gun (with everything I could removed) and after 30 minutes a bubble did form at the edge of the high pressure gauge right where the glass crystal and the chrome housing meet. Given the position of this leak, it is no wonder that it was not caught by any previous technician or servicing. New Wika gauge installed and after three days, no change in pressure.
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