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Author Topic: crosman 1377 leaks  (Read 613 times))

Offline cooter303

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crosman 1377 leaks
« on: March 07, 2021, 08:07:56 PM »
Crosman 1377. leaks at the breech. I put a new transfer port seal in and it still leaks. The plastic breech was bubbad from precious owner so I put a steel breech on it. Kept the factory barrel on it. Not sure if there is an issue there or not.
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Offline Bentong

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Re: crosman 1377 leaks
« Reply #1 on: March 07, 2021, 11:45:00 PM »
If you feel blast of air to your face, it's the bolt o-ring..otherwise the TP seal is upside down
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Offline cooter303

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Re: crosman 1377 leaks
« Reply #2 on: March 08, 2021, 12:49:11 AM »
If you feel blast of air to your face, it's the bolt o-ring..otherwise the TP seal is upside down

Its leaking to the side. Did the tissue test. How is the seal put in? I have the seal in, then the transfer port with short end down. Thats how it looks in the parts diagrams.
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Offline Rick67

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Re: crosman 1377 leaks
« Reply #3 on: March 08, 2021, 02:04:43 AM »
I reinforce the the TP (top section) with a small and thin O-ring from a disposable lighter.

What do you mean by leaking?

Does it leak as you pump it?

Check your valve and probe O-ring too.

The 13xx is one of the easiest airguns to work on.
  • Abq., NM, USA

Offline cooter303

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Re: crosman 1377 leaks
« Reply #4 on: March 08, 2021, 07:09:37 AM »
it leaks when I fire it. Only getting around 350 fps with 10 pumps. From some reading I have done, I have the wrong transfer port for the steel breech to seal. So will try and get the proper port or try and find an original breech for it. I have also read about using some ice maker tubing to make a port.
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Offline Rick67

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Re: crosman 1377 leaks
« Reply #5 on: March 08, 2021, 07:43:01 AM »
The TP is the same for both plastic and steel breeches.

Try the O-ring mod on the top section of the TP.

You could also put a disposable lighter O-ring behind the probe O-ring to make the sealing better.
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Offline Rick67

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Re: crosman 1377 leaks
« Reply #6 on: March 08, 2021, 07:45:01 AM »
Cover the lighter with towel as you smash it with a hammer because it will explode a little bit.
  • Abq., NM, USA

Offline Spooner

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Re: crosman 1377 leaks
« Reply #7 on: March 08, 2021, 08:04:36 PM »
if you are using the transfer port from the original gun, or one that is listed for the 1377/1322 platform... they are the same and are correct for either platform with either the plastic or steel breech. is there maybe a gap between the breech and the pump tube? if the breech isnt seated completely (meaning no visible gap between them), that could cause your leak as well.  ;)
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Offline cooter303

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Re: crosman 1377 leaks
« Reply #8 on: March 08, 2021, 08:40:46 PM »
I will try a little O ring on top of the transfer port. This gun was leaking there with the old plastic breech. The previous owner buggered up the plastic breech, so I had to put the steel breech on. This gun has been a thorn since I got it!! In the meantime. I broke down and bought a new 1322. Its spitting out a 22 cal pellet at 450 to 460 fps with 10 pumps. I had put walnut furniture on the 1377 and Iam transferring it over to the 1322. The black plastic just doesnt cut it. Crosman should have stayed with the imitation wood at least!!!
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Offline Bentong

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Re: crosman 1377 leaks
« Reply #9 on: March 08, 2021, 11:07:59 PM »
I will try a little O ring on top of the transfer port. This gun was leaking there with the old plastic breech. The previous owner buggered up the plastic breech, so I had to put the steel breech on. This gun has been a thorn since I got it!! In the meantime. I broke down and bought a new 1322. Its spitting out a 22 cal pellet at 450 to 460 fps with 10 pumps. I had put walnut furniture on the 1377 and Iam transferring it over to the 1322. The black plastic just doesnt cut it. Crosman should have stayed with the imitation wood at least!!!
Something to look for is if the barrel is centered to where the tp hole is located located looking under the removed breech. The long end of the TP should be able to blast the air else if not centered goes sideways of the breech. Also make sure the black rubber seal is on the short end of the tp when you insert it towards the valve. 👍
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Offline cooter303

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Re: crosman 1377 leaks
« Reply #10 on: March 09, 2021, 02:37:50 PM »
yup. Thats all good. Will try a little O ring on top and see how that works. Will get this 1377 working properly one day!!!
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Offline cooter303

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Re: crosman 1377 leaks
« Reply #11 on: March 11, 2021, 03:10:22 PM »
Well I took it apart and was able to put another transfer port seal on top and put it back together. Done the tissue test and no leaks. Will run it through the chronograph this afternoon.
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Offline cooter303

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Re: crosman 1377 leaks
« Reply #12 on: March 11, 2021, 07:04:03 PM »
Well still not right. Getting only 375 to 400 fps with 10 pumps. I think I will keep it for parts. Has never worked right for me since I got it!!!!
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Offline Rick67

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Re: crosman 1377 leaks
« Reply #13 on: March 11, 2021, 10:10:24 PM »
Well still not right. Getting only 375 to 400 fps with 10 pumps. I think I will keep it for parts. Has never worked right for me since I got it!!!!


Try swapping the valve.
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Offline cooter303

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Re: crosman 1377 leaks
« Reply #14 on: March 11, 2021, 11:23:22 PM »
Will give that a try Rick. I see some on ebay. I bought a new 1322. Should be able to put a modded valve in it and put the valve from the 1322 into the 1377.
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Offline Ramrod1948

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Re: crosman 1377 leaks
« Reply #15 on: March 18, 2021, 02:25:22 PM »
Make a new transfer port from refrigerator tubing. Plenty of info on web on how to do it.
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