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Leaking hose fittings on unloader

352 Views 15 Replies 3 Participants Last post by  stevon, 
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Hi All,
I am trying to sort out a Devillbiss Pro 4000 compressor. I believe the model number is RA350E30AD.

The issue that I am currently having involves the tube that travels from the lower end of the manifold and up to a needle valve. I believe that the needle valve activates the switch to start the compressor when tank pressure drops too low, but I am quite new to this machine.

The compressor arrived with a nylon (or some other plastic hose going from the low end to the needle valve. It was leaking badly when I got it, so I have tried different combinations of hoses and connectors, including the type used on a 1/4” water supply to a fridge (hose seems to be the same size).

In every case I have had a leak — usually the hose pops off of one end or the other. I finally thought I had it solved by using some fittings typically used on air shocks, but they are leaking too…

Any suggestions will be welcomed. I have a pressure switch from another dead compressor. Is it worth trying to ditch the hose setup in favor of a an electric pressure switch?

And while I waited for this thread to be approved, I just read another thread in which the check valve was the culprit. I will look into that this morning, as the hissing/leaking is constant after filling, not just a few seconds.


Thanks,
David


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This is becoming more of a reference thread as I have received no responses but may be on the verge of solving the issue myself.

Based on threads I have read on this forum, I began to suspect that the issue is actually the check valve. A short while ago I removed the manifold (the check valve is in the base) and inspected the check valve.

A visual inspection was not enough, so I pulled the plastic end off, freeing the stopper and spring. That is when I discovered the issue… the spring had snapped in half, meaning the stopper would never actually move all the way to close the valve.

I am headed to the hardware store to replace the spring. Hopefully, by tomorrow this compressor will be functioning as it should :)

Thanks,
David

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F
If you're describing what I think you are the pilot valve (needle) is releasing air from the check valve that's leaking. The pilot valve decompress the cylinder so the motor isn't working against compressed air on the next cycle.
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Hi Flop,
That is what I am thinking, and I have pulled the check valve and found a broken spring…

Thanks,
David
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Now I am wondering about the importance of the exact tension of the spring…

Thanks,
David
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Hi All,
It worked! Pressure on this new-to-me compressor holding steady at 109 psi.
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F
Couple turns of that larger nut might get you a few more pounds if you need it.
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Hi Flop,
Thanks — that is the kind of info I need! I am fairly new to these larger compressors with this type of pressure switch.

Thanks,
David
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stevon
2002sheds,

It sounds like your check valve is leaking from tank back pressure. check valves always eventually fail and are a cheap maintnence part like the air filter that occasionally needs to be replaced, Grainger can help you out, just bring in the old one to match up.

Stephen
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Stephen
2002sheds said:
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stevon
flopshot,

Don't go too far, your tank label is stamped with maximum working pressure (WP) so don't go over that! 155 psi WP is typical for single stage compressors.

Stephen
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flopshot said:
Couple turns of that larger nut might get you a few more pounds if you need it.
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2002sheds said:
Hi Flop,
Thanks — that is the kind of info I need! I am fairly new to these larger compressors with this type of pressure switch.

Thanks,
David
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That switch has a basic on/off range that can be tweeked a few psi in either direction if necessary. The smaller spring assembly on the left in your photo is the "on" setting. Tighten to raise the point at which the motor comes on, tighten the larger one to raise the "off" setting. Do you have a pressure relief pop off valve ? Small brass fitting that might have a ring in it. It releases pressure if the switch fails. Also, there should be a tank moisture drain in the bottom of the air tank.
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Hi Flop, Stevon,
Noted about the high pressure. Stevon, I have already pulled the manifold (check valve in base) and replaced the broken spring. The compressor has been holding almost perfectly steady for several hours now, losing only about 3 pounds in that time.

Thanks,
David
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stevon
David,

A check valve is a maintenance part and is readily available and relatively cheap they do wear out and leak, my self I wouldn't rebuild one but if it works for you kudos!
There should be 0 leakage from a good/new check valve, just make sure compressor has no power when not it use!

Stephen

2002sheds said:
Hi Flop, Stevon,
Noted about the high pressure. Stevon, I have already pulled the manifold (check valve in base) and replaced the broken spring. The compressor has been holding almost perfectly steady for several hours now, losing only about 3 pounds in that time.

Thanks,
David
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Hi Stevon,
I couldn’t find the check valve for this compressor (the part is integrated into the manifold and had been discontinued), so I resorted to fixing it with a 69 cent spring.

Thanks,
David
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stevon
David,

That's too bad about there being no replacement check valve available, parts sometimes do become unavailable especially if it fits only one type/brand of compressor. Sometimes there is a way to plumb in another type of check valve but sometimes not! At least your machine is still in use and not contributed to waste/land fill lol.

Stephen

2002sheds said:
Hi Stevon,
I couldn’t find the check valve for this compressor (the part is integrated into the manifold and had been discontinued), so I resorted to fixing it with a 69 cent spring.

Thanks,
David
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