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Re: Leaking piston?
Yes - definitely check the hose connections first (sorry - I should have mentioned that to begin with, but mistakenly assumed that those were already known to be good). If the hose connectors are leaking, it will usually be from one of four problems:
1- the brass fitting/connector is not seated all the way down in the fitting hole in the piston. Make sure it is tightly wrenched into the fitting hole, and bottoming out on the connection.
2- forgetting to use teflon tape on the fitting threads. The brass-to-aluminum seal between the fitting and piston is not completely airtight by itself. You must use teflon tape (or a suitable alternative thread sealer) to completely seal the joint. One wrap completely around the threads is all that is needed. Too many wraps of the tape are just as bad as not enough.
3- the pneumatic hose is not seated all the way into the connector fitting. Be sure and push the hose into the fitting, past the little "bump" you will feel, and all the way to the bottom of the fitting (note: the pneumatic hose must end in a nice, clean, square cut to seat properly - do not have an angled or ragged cut at the end of the hose)
4- debris or foreign materials may have fallen in to the connector, preventing a good seal. Make sure the connector is clean and empty. Shake out any foreign material (and don't do things like drilling metal right next to an open connector, where the chips may fall in to the pneumatics).
To check and be sure where the leak is actually located (connector or piston seal), pressurize the piston and swab some very soapy water over all the joints. The leak will be easy to spot, as it shows up as a series of bubbles.
Your original message said that the leaks seem to be happening when the piston hits a mechanical stop before reaching the end of the full stroke. Does the leak also happen when the mechanical stop is not present, and the piston extends normally? If so, then I would look for a connector leak first. But if the leak only happens during an interupted stroke, and not at full stroke, then I would start to suspect a bad piston seal.
-dave
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Last edited by dlavery : 23-03-2004 at 09:29.
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