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[HELP] Pneumatic Pump Issue

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Hi everyone

I need some help to troubleshoot an issue that I'm having with a Pneumatic Pump.  It has a leak, but I don't think that it is the piston or the one-way valve.  I think that there may be a tiny hole in the black casing.

Please watch this short (2 min) video for details:

Has anyone experienced a similar problem, or have a solution?

I was thinking that I could use some glue (hot glue / super glue / two-part epoxy) to block the hole, but I didn't want it to seep in and block the air flow completely.

I've had this pump for a few years, but I think this is the first time that I have actually used it.  If this is a manufacturing defect, do you think Lego would replace it?

Any advice would be appreciated.  Thanks.

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That's some good detective work. It looks like the leak is in the check valve.  This should allow air into the cylinder on the upstroke, but close after that. It doesn't appear to be closing completely. 

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"If this is a manufacturing defect, do you think Lego would replace it?" I would say so. A pump is not supposed to leak of course and especially not at the bottom.

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Certainly looks like a tiny pin hole leak/crack/manufacturing defect in the bottom black casing. I am fairly confident Lego will replace it for you. If not then a tiny dab of superglue should fix it. Just be careful as capillary action will pull the glue down into the tiny imperfection (which is a good thing) but too much will cause superglue to be inside the pump, which obviously isn't good.

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Thanks everyone for your feedback and suggestions.

I decided to get out my macro lens and a close-up filter for my camera to see if I could take a picture showing the hole/crack.

Keep in mind that the width of the pneumatic pump is only 7.9mm (0.31"), so the crack is really tiny, but still allows air to leak.

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I know that I've already shown the leak in the video in my initial post, but another way that I tested for the leak was to pressurize the system and hold the pump up to my ear.  The air coming out can clearly be felt on my ear lobe and ear drum (obviously don't do this with high pressure or high volumes or air).

I have contacted Lego's Broken Pieces service for a replacement.  Their website says that they don't have this piece in stock and they may offer an alternative, but they should respond within a few days.

In the comments of my YouTube video I got the following suggestions:

  • tape - I don't think that tape will be able to handle the pressure of Lego Pneumatics (up to about 45psi).
  • hot glue - I love hot glue, but it isn't the best at sticking smooth surfaces together.  It doesn't react with materials, but rather the hot glue seeps into fibers of materials and, once cooled, friction holds it in place.
  • superglue - This is usually a thin liquid, so it will seep into the crack using capillary action (as allanp mentioned).  It is not a 'filler', but the crack that I have is so small that I think it will work ok.
  • two-part epoxy - This is a lot thicker than superglue and can be used as a 'filler', but I don't think that it will seep into the crack too well.

Maybe I could use some superglue and, once that is cured, I could add a thin layer of two-part epoxy over the top of it.

I'll wait until I hear back from Lego before doing anything else.

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That was a very interesting and thorough investigation.  (I don't think I've ever seen a Lego part that close up!)  I hope you get it sorted...

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I hope you get a replacement part, but it does show to all of us how well the Lego parts, particularly the pneumatic elements, are manufactured in the first place.  I have some problems with my pneumatics, and I hope I can problem solve as well as you. 

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When troubleshooting pneumatics it is usually a matter of isolating elements to work out which elements work and which ones don't.  Having the manometer helps a lot too.

I submitted a request to Lego's Broken Piece Service, but I just got an automated message back saying that the part is no longer available, and my request was cancelled.

I have now submitted an email to Lego (that hopefully a person will read and action) asking if I can get a replacement or a substitution for a similar part.  And now I wait again...

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Last week Lego sent me a replacement pump, so I have tried to fix the old faulty pump.

Hopefully the tiny drop of Super Glue will be a long-term solution.

Thanks to everyone on Eurobricks and YouTube that provided comments and suggestions.

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On 1/28/2017 at 3:09 PM, Cornersruns said:

To add filler to superglue use baking powder, sprinkle a little on the add superglue.

Thanks Cornersruns, however in this case I didn't want to use any filler or thick glue as the crack in the Pneumatic Pump was so small.  I wanted to rely upon capillary action to draw some of the thin Super Glue into the crack.

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I have had this exact problem - same pump, same set too. From that set as well my large hand pump has developed issues to the point of squealing horribly when depressed and taking a very long time to return to the neutral position. I've not had issues with any of the other parts from the Education pneumatics set!

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Only problem I've had with older pneumatics are the old studded switches that start to leak.

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