FX FX Crown, Can't find leak

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sobdiver

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Dec 25, 2020
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St. George, UT
My FX Crown has a slow leak, about 2 bar/day - over 10 bar per week. I have leak detector fluid and have removed the stock at least 4 times looking for the leak over and over without success.

IMG_7830_.jpg

I've checked the base of each gauge, the foster fill nipple base, fill nipple exit, all around the regulator, including the vent hole on the side,

IMG_7831_.jpg

checked the plenum plug

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Checked the valve plug/cover

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Checked all around the bottle

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And have done the baloon test. (above pick after about 15 hours)
IMG_7835_.jpg


Help. What am I missing???
 
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yeah, but bubbles can be tricky .. not sure about 'leak detector' but i always use a dab of dish soap in a bit of water in a cup .. swish it around with a qtip and apply that way .. its not always instantly apparent, but at some 'critical mass' point of evaporation the bubbles will grow a little mass thats easy to see, so dont flood it too much with the solution is the point .. just swab it on suspect points and keep an eye on it for a few ..
 
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dizzums said:
yeah, but bubbles can be tricky .. not sure about 'leak detector' but i always use a dab of dish soap in a bit of water in a cup .. swish it around with a qtip and apply that way .. its not always instantly apparent, but at some 'critical mass' point of evaporation the bubbles will grow a little mass thats easy to see, so dont flood it too much with the solution is the point .. just swab it on suspect points and keep an eye on it for a few ..
Click to expand...
I've found leaks before with the leak detector. It usually bubbles up obviously, probably better than soap and water.
 
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SilentSquirrel said:
If a regulator in a Crown is leaking from where does the air exit?
And how can it be detected?
Hoping to learn!
Edward
Click to expand...
sobdiver said:
I do have a current Crown MK II (less than a year old) with I believe the latest AMP regulator. Yes, I should get bubbles somewhere if it were leaking, right?
Click to expand...

In my recent experience with a (Mk1) Crown with a leaky AMP regulator, I was getting bubbles from the center of the reg, around the adjustment set screw. Depending on the o-rings which are bad, leaks from the reg can also be seen from the outside thread of the reg, and/or out of the hole in the side of the block. This is what I have recently, personally seen, and may not be all encompassing.

And yes, leak detector and a balloon are your key tools to finding the leaks. As suggested by another member, a few drops of dish soap in water in a spray bottle can be used as well - in a pinch. But I concur with the OP - If looking for pneumatic leaks, use a real, quality leak detector spray!

Sorry OP - other than agreeing with your methodology I can't provide you any real solution to your issue.

I agree with another member that reg leaks, if that is what is found, can be tricky to solve. I tried first by replacing the AMP regulator with the correct HUMA reg. And it leaked badly. Fortunately later I found another AGN member selling 2 old AMP regs which he had replaced out of his Impact or Crown. I bought them and one of them fixed the leak (the other one didn't). So there are apparently some dimensional differences in the regulator 'pocket' of these guns and fixing leaks can become more art than science.

Stealing the OP's photo:
Crown Leak_.jpg
 
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TMH said:
In my recent experience with a (Mk1) Crown with a leaky AMP regulator, I was getting bubbles from the center of the reg, around the adjustment set screw. Depending on the o-rings which are bad, leaks from the reg can also be seen from the outside thread of the reg, and/or out of the hole in the side of the block. This is what I have recently, personally seen, and may not be all encompassing.

And yes, leak detector and a balloon are your key tools to finding the leaks. As suggested by another member, a few drops of dish soap in water in a spray bottle can be used as well - in a pinch. But I concur with the OP - If looking for pneumatic leaks, use a real, quality leak detector spray!

Sorry OP - other than agreeing with your methodology I can't provide you any real solution to your issue.

I agree with another member that reg leaks, if that is what is found, can be tricky to solve. I tried first by replacing the AMP regulator with the correct HUMA reg. And it leaked badly. Fortunately later I found another AGN member selling 2 old AMP regs which he had replaced out of his Impact or Crown. I bought them and one of them fixed the leak (the other one didn't). So there are apparently some dimensional differences in the regulator 'pocket' of these guns and fixing leaks can become more art than science.

Stealing the OP's photo:
View attachment 474256
Click to expand...
Thanks for the arrows and your help/assistance. I'm confident that the gun is not leaking where you have the arrows as I have tried many rounds of leak detector on those spots.
 
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Like TMH said above, an airgun service friend and I tried many different regs old (serviced) and new, almost the reg threads wouldn't fit in the receiver so we ended up sending it to FX during their legal issues and they didn't have regs that would fit/work so they just replaced the whole receiver with new reg....friend said that he has seen that with a few FX Crowns. Great guns, they just need to be more consistent in their machining.
 
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Bill_D said:
I see you have a balloon on the end of the barrel - is this how you're checking the valve? - if there is a bad ring on the valve or in the valve stem or just dirty - it can leak out the breech and not the barrel. Pretty hard to check without removing the valve.
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Yes, using the balloon to check for a valve leak. I seem to have eliminated leaks that are externally findable with leak detector solution. If the valve can leak without inflating my balloon, then the leak might be getting narrowed down to the valve. Maybe replace the valve stem and valve seat and see what happens?
 
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sobdiver said:
My FX Crown has a slow leak, about 2 bar/day - over 10 bar per week. I have leak detector fluid and have removed the stock at least 4 times looking for the leak over and over without success.

View attachment 474153
I've checked the base of each gauge, the foster fill nipple base, fill nipple exit, all around the regulator, including the vent hole on the side,

View attachment 474155
checked the plenum plug

View attachment 474156
Checked the valve plug/cover

View attachment 474157
Checked all around the bottle

View attachment 474158
And have done the baloon test. (above pick after about 15 hours)
View attachment 474159

Help. What am I missing???
Click to expand...

Remove the bottle and dunk just the bottle into a bucket of water to see if the valve is leaking. In all your tests you never mentioned the fill QD, and that is also a leak point. The inner check valve piston has an o ring that seals the pressurized air from coming back out. That o ring can either dry up or get debris caught up in it, not allowing the o ring to do its job
 
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Airgun Al said:
I would also agree with TMH, and perhaps re-test the area with the top yellow arrow, in his previous post (#9) above.
If not there, I would exercise the factory warranty, ship the action only, back to U.A, and probably have it returned better than ever.
Good luck.
Click to expand...
Thanks, I've put drops of leak detector in that hole by the top yellow arrow every time I"ve removed the stock to once again try and find the leak.
 
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Bigragu said:
Remove the bottle and dunk just the bottle into a bucket of water to see if the valve is leaking. In all your tests you never mentioned the fill QD, and that is also a leak point. The inner check valve piston has an o ring that seals the pressurized air from coming back out. That o ring can either dry up or get debris caught up in it, not allowing the o ring to do its job
Click to expand...
Yes, I've checked the fill QD many times with drops of leak detector. I think in my writeup I called it the "fill nipple exit" lol
 
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My mk2 crown had a very slow leak. I’ve learned that if the balloon doesn’t inflate at the end of a barrel with slow leaks, there’s four areas I focus on on these types of leaks- bottle and bottle connection, gage threads (or the gages gone bad), the QD connection for air fill, and lastly the reg vent hole. I never drop any leak detection fluid into a reg vent hole. It’s not meant to have fluids in there. But instead, put a strip of electrical tape over the hole and push down on the tape over the hole to create an “insey”. If after an hour it becomes an outsey with a bubble then you have an o ring that has failed in the regs or the reg tunnel. If it takes forever for a bubble to happen then that’s normal venting of the reg with temp fluctuations.

On the other areas I’ve listed, I use leak detector but put a drop of the solution with a tiny q-tip or toothpick, and shine a flashlight light into the seams looking for the tiniest of bubbling. Just dousing or spraying seams with leak detection on slow leaks won’t work, as leak solutions wether liquid or spray form their own bubbles which can be deceiving.

On the bottle to rule out the valve I just dunk the bottle itself in a bucket of water. That’s where my leak came from so that was an easy fix. If the bottle valve is good, reinstall the bottle then drizzle a drop at the bottle connection to see if the Dowty seal has gone bad.


Keep in mind, over lubing of o rings even if new, can cause an o ring to roll off of its groove once pressurized with air, and cause a leak. Rubbing alcohol or acetone will clean off parts of extra lubes, just be careful with using acetone on plastic parts.

If you ever used steel o ring pic tools to pry off old o rings and you scratched an o ring groove, well, there’s nothing that’s gonna fix that. Consider that part toast. Always use plastic or brass pic tools instead
 
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Bigragu said:
My mk2 crown had a very slow leak. I’ve learned that if the balloon doesn’t inflate at the end of a barrel with slow leaks, there’s four areas I focus on on these types of leaks- bottle and bottle connection, gage threads (or the gages gone bad), the QD connection for air fill, and lastly the reg vent hole. I never drop any leak detection fluid into a reg vent hole. It’s not meant to have fluids in there. But instead, put a strip of electrical tape over the hole and push down on the tape over the hole to create an “insey”. If after an hour it becomes an outsey with a bubble then you have an o ring that has failed in the regs or the reg tunnel. If it takes forever for a bubble to happen then that’s normal venting of the reg with temp fluctuations.

On the other areas I’ve listed, I use leak detector but put a drop of the solution with a tiny q-tip or toothpick, and shine a flashlight light into the seams looking for the tiniest of bubbling. Just dousing or spraying seams with leak detection on slow leaks won’t work, as leak solutions wether liquid or spray form their own bubbles which can be deceiving.

On the bottle to rule out the valve I just dunk the bottle itself in a bucket of water. That’s where my leak came from so that was an easy fix. If the bottle valve is good, reinstall the bottle then drizzle a drop at the bottle connection to see if the Dowty seal has gone bad.


Keep in mind, over lubing of o rings even if new, can cause an o ring to roll off of its groove once pressurized with air, and cause a leak. Rubbing alcohol or acetone will clean off parts of extra lubes, just be careful with using acetone on plastic parts.

If you ever used steel o ring pic tools to pry off old o rings and you scratched an o ring groove, well, there’s nothing that’s gonna fix that. Consider that part toast. Always use plastic or brass pic tools instead
Click to expand...
Thanks for the good info. I removed the bottle and did the dunk test - no bubbles. FWIW after I've put leak detector solution in the reg vent hole, I've then rolled a small piece of toilet paper between my fingers into a sharp tip, inserted into hole and soaked the fluid back out, same with the QD connection. Also, out of the box my crown had a gauge that was leaking at the threads and it was easy to find the leak with the leak detector solution. As I tightened the gauge to stop the leak I was able to still detect the leak as it got smaller and smaller. So, I'm pretty sure if there was a leak like that now I would be able to detect it with the amount of times I've tried. Bill_D stated that if the leak is at the valve it can leak out the breech without inflating the balloon. Can anyone verify if that is the case?
 
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sobdiver said:
Моят FX Crown има бавен теч, около 2 бара/ден - над 10 бара на седмица. Имам течност за детектор на течове и съм свалял запаса поне 4 пъти, търсейки теча отново и отново, без успех.

View attachment 474153
Проверих основата на всеки габарит, основата на нипела за пълнене на Foster, изхода на нипела за пълнене, навсякъде около регулатора, включително вентилационния отвор отстрани,

View attachment 474155
провери щепсела на пленума

View attachment 474156
Проверих щепсела/капака на клапана

View attachment 474157
Проверено навсякъде около бутилката

View attachment 474158
И направих теста с балон. (избор по-горе след около 15 часа)
View attachment 474159

Помогне. Какво ми липсва???
Click to expand...
IMG_7830_.jpg


Концентрирай се върху оградената зона. Оттам открих теч както при теб много малко за дълго време, смених един опръстен на регулатора и теча се прекрати.
 
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