Cleaning a Leaky HVLP Gun

Air bubbles leaking into the cup indicate the need for a thorough cleaning. September 11, 2006

Question
Air is leaking into the cup on my HVLP spray gun. Just a constant stream of bubbles coming up when I trigger the gun. And of course, the gun's sputtering. Help!

Forum Responses
(Finishing Forum)
From contributor D:
It sounds like you have a clog in the horns of your air cap and/or the opening of the fluid nozzle of your gun. The air has to go someplace, following the path of least resistance, so it goes up through your liquid in the cup.

Get out some wooden toothpicks and soak the air cap and fluid nozzle in acetone. Brush them with an acid brush and/or a toothbrush. Use the toothpicks to probe and pick at the holes to clear any blockages.

Once the gun parts are clean and reinstalled, and the leak is fixed, clean the air cap after every one or two panels that you shoot. Use the acid brush dipped in acetone to dab the front of the air cap of any fresh accumulations.

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From contributor S:
Buildup on the cup gasket can cause that, too. It doesn't take much for air to start leaking. A little mineral spirits should take care of it.

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From contributor E:
Normally, this is caused by a loose nozzle or air cap. In fact, I do this intentionally to perk the gravity guns I have during cleaning. Make sure the air cap and the nozzle are tight, and under normal circumstances, this will fix it. On the earlier model of the Astro HVLP-DX guns, there was a very small Teflon gasket on the nozzle that was very easy to lose. Once this happened, bubbles and sputtering was the norm.