Tuning pp700sa slow leak

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Barzor

Member
Dec 27, 2021
88
13
Manila, Philippines
it seems that every time I open up the pistol or do some kind of mod where I have to de-gas I notice that after filling and letting it sit for 48 hours the pressure goes down to the beginning of the green level, it should be at the end of green almost red.

I have tried listening for the leak no luck, I have tried spraying with soapy water the areas common for leaks no luck either.

I almost feel that I have to change all the o-rings but this would be a waste too since they are all new. I have only fired maybe 30 shots from this pistol.

Can someone help me again...
 
There should not be a leak there since i bypassed the reg and using huma reg. Also Im too scared of removing the barrel as I have heard stories of barrels just turning.

When I bought the gun new there was never a leak it would have full air all week. Only when I started tinkering with the air tube, regulators and valve. I never touched the barrel.

If I were to guess it would be somewhere between the air tube old regulator and the part of regulator that goes into breech.

I noticed that when I first disassembled there was a lot of gun lube or o-ring silicone lube. would this help with leaks?

Can i submerse the entire gun in water?






 
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What all did you do with the valve?
20220107_233803.1641624394.jpg



 
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Often times when you take a gun apart and leave it apart for more than 10 mins the orings expand and take a new shape. I have had to replace all the rings on a few guns from that mistake. New rings haven't had pressure on them and deformed. Also the barrel might spin but you just have to angle it properly and it will go into place. Its a pain but not a permanent breakage. I deal with it still to this day. Some people drill holes in the receiver and tap them for set screws to hold the barrel in place to stop wiggling around. It helps with accuracy and allows you to put a moderator on without unscrewing the barrel every time.....ask me how I know.
 
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The leaks I have observed on multiples of pp’s have all been at the fill port, really slow ones. I didn’t catch it initially until I built a sealed dust plug for them, after an hour, they had so much pressure on them you could hardly pull them out, when you did, you would hear a sharp air snap. Pretty easy to fix those thank goodness👍🏻 But I would look hard there.
 
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Thanks guys for all the info I think ill replace all the orings from front of air tube to the trigger all the bottom end. I thought the dust cover is the cylinder that rotates and covers the fill hole. SO you guys are also saying that air leaks out of that hole???

Can someone explain, ive never seen video or explanation of how high pressure air is hand pumped or compressored into the air tube. Is it like inflating my vehicle tires where that little pin is pushed down while air is being pushed in and the pin goes up to close and prevent air from leaving?

How does the probe keep the high pressure air from coming back out, is there a one way valve or flap that keeps air in and is it this flap that is leaking?
 
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Yupp, basically a one-way flap. It's the part no. 34 in the parts diagram attached below.

The other issue that caused a leak when I installed the Huma was that part no. 29 wasn't screwed in tight enough.

Some others have reported that part no. 31 had inadvertently flipped around and didn't seal well — or that it was not sufficiently tight installed to seal well.



Matthias



Attachment:

PP700S-A exploding parts diagram

download.png
View attachment Parts. Diagram. From www.Milidonis.gr. PP700S-A. 2019.1641708860.pdf


 
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Yeah sometimes a small piece of dust or grit will get into the flap that operates as a check valve. Sometime you can take it apart and clean it and other times you need to buy another part and replace it. I wouldn't submerge it completely unless you plan on taking it apart and clean dry and lubricate everything. Try everything else b4 that.
 
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These guns leak like sieves from the factory. for several reasons. The first being very poor quality O rings. The second is that no silicone lube is used during installation/assembly at the factory and in my case, on my second P700S-A, the anodizing around the inside of the tank fill port started flaking off. I think incorrect metal prep before anodizing was the cause. In every case just changing the O ring solved my issues. I have never had a European O ring fail, only the crap Chinese O rings from Snow Flake! It is very important to be very careful installing the large tank O rings at both ends of the tank tube (28mm?). Be sure to use silicone oil on the wall of the tank and the O ring itself, that O ring is easy to damage.

The fill check valve is a simple screw with small flats milled on the side for air flow. Fill pressure pushes against the back face of the screw allowing the screw to slightly lift off the sealing O ring. When the tank is full and fill air pressure is removed, the tank pressure causes the screw to reseal on the O ring. When leaks occur there, it is usually because the crap O ring lost its resilience..
 
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THANK YOU EVERYBODY FOR ALL THE ADVICE:

I bought the o-ring replacements pack for pp700sa from an airgun store where I live. It had all the stock o-rings including different colors such as green and brown. Then I measured all of them up, looked up the sizes on the parts diagram and ordered from the O-ring store lots of replacement 70 buna o-rings. Now I have a set of originals and many sets of the better ones. I them took apart the pp700sa and changed all the o-rings including the one in air tube under a crew for the fill port. The original rings looked OK non chewed up but like someone said that when they are in the air they change shape. LUCKILY after changing I have no leaks. I check overnight and still at the gauge at the same spot it did not move.

One thing thou. When i did some test firing I noticed that the o-ring at the breach face comes out, its good that the swing breech block prevents it from totally flying off, but I just push it back in place. Its the one that is supposed to be green. Im using a black o-ring of the same size. I did put o-ring lube on it, would that cause it to be blown off????
 
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SO I replaced all of the O-rings in the pp700sa with new ones from oring store thanks to all the info from the forum. I thought I had fixed the problem but when after 2 weeks I see a 1 line on the gauge go down, by a month there is 3-4 lines down. I don't get this. Luckily I only shoot till I runout of air or down to 10 bar. then refill. I never see this decline of air though when I'm using the pistol only when I let it sit for a few weeks.

Today I decided to drop half of the pistol into water to see if there are bubbles. I submerged were everybody pointed to between air tank and trigger, the silver round piece, the valve.

To great disappointment NOTHING no bubbles not even small one, or bubble growing. I'm so disheartened as I know I lubed all the orings and put better quaity that the stock orings.

What should I try next???
 
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These pistols are a Chinese product. They are made to a price point and in doing so, shortcuts are taken. So, there is always a risk that dimensions are out of spec. I really like my PP700SA, but they do tend to leak. Yes, you have a leak, but it doesn't hurt the use of the pistol however annoying it may be. If you elect to solve all leaks, you will need to check all the dimensions surrounding every O ring. You may find as I did some dimensions too large either in depth or ID or OD. This is not an issue though, as O rings slightly larger than standard are available. See my previous posts.
 
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