mark.bitterlich(at)navy.m
Guest
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 Posted: Tue Aug 02, 2016 8:39 am Post subject: [Non-DoD Source] Re: Snot Valve Not Snotting... |
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Before I had any experience with what "usually" fails, I had this very same exact problem. Given that it is hard to hear leaks with the engine running, I decided I needed some other way to pressurize the system and find where the leak was. I did this by obtaining a regulator and an air source where I could attach 700 PSI of air into any point in the system I wanted. Since I made this rig, it has been invaluable numerous times. Emphasis on having a good regulator!
After the snot valve, the air line goes up to a central fitting where there are check valves and also the over pressure relief valve, or "pressure regulator" if you will. The brass fitting with rubber end and spring deal, that if you don't know intimately now, you soon will.
Detaching that and pressurizing the line BACKWARDS, forcing air back towards the compressor quickly found the problem. The "output check valve" on the compressor, I.E. Exactly the one Walter was talking about. The next time it was the Banjo Fitting that is also part of that whole "output check valve" mess. Why? Because I did not replace the aluminum crush washers the FIRST time I repaired it. Lesson learned.
Yes, I have had the snot valve leak as well, but always to where I could hear it as soon as I shut the engine down. Never-the-less, reverse pressurizing the line proved that one too.
I despise being reduced to 'dive bombing" or "shot-gunning" a problem. When I have an electrical problem, I go grab a meter, a scope, a watt-meter, whatever. Just like not running for a crescent wrench and instead having a good set of wrenches in EVERY size!  My point is that when you have an airplane that incorporates compressed air for a number of different functions (flaps, gear, brakes, etc.) it is incombent on even a backyard mechanic to have some tools to deal with it. Making something like this is not exactly "trivial", but it is a necessary addition to Yak and CJ aircraft owners who desire to do their own troubleshooting. Otherwise, get used to "changing shit" and then wondering whether you just fixed it, or made it even worse.
Mark
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From: owner-yak-list-server(at)matronics.com [owner-yak-list-server(at)matronics.com] on behalf of Rico Jaeger [rocknpilot(at)hotmail.com]
Sent: Tuesday, August 02, 2016 11:30 AM
To: yak-list(at)matronics.com
Subject: [Non-DoD Source] Re: Snot Valve Not Snotting...
| Quote: | From someone who's been down this road so many times they named the street after me...you said the system seems to be operating normally other than the snot valve? So if your gauges are registering air pressure regeneration, the compressor is doing its job. The snot valve can be finicky in that it can easily develop reasons to incompletely close - either from basic wear & tear to needle valve obstructions to just accidentally being left partially open. If this were the case, there could still be enough closure to build pressure but just enough seepage to continuously clear the valve. Whatever the case, ripping the system apart is a pain. The 3' tall line workers with the 11" fingers that built these planes musta smirked every day when pondering we Westerners trying to dig into the many dark nooks & crannies with our sausage digits. I would highly suggest you start with the simplest options in your trial / elimination process before cutting too much safety wire. Always happy!
to pass on what I've learned here, but far from the level of the masters like Dennis, Jill and Doug.
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Sent from my iPad
[quote] On Aug 2, 2016, at 9:52 AM, Walter Lannon <wlannon(at)shaw.ca> wrote:
Compressor. Start with the output check valve.
Ot valve
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