Slow leak on Champion VR5-8

My air compressor, a 20 year old Champion VR5-8 leaks air out of the rubber hose used to release pressure from the pistons after the power shuts off.

The hose connects to what looks like some kind of diaphragm body (second picture) and dangles down along side a thin copper tube coming from near the bottom of the tank. the air coming out of the hose is easily detect able though I can't hear a hiss, but when I put my finger over the tube it builds pressure and pops off.

I read a lot of posts about check valves being responsible for likes, but I am not that familiar with large air compressors like this. The parts list mentions, I think, three check valves. How do I know which valve needs to be replaced? I am assuming that the air from the tank is either leaking back through the main inlet line through the pistons, and through the diaphram thing back to the hose, or it could be coming out of the thin tube connections to the diaphragm thing and out from there.

Suggestions?

Not familiar with that particular model. Many compressors have an unloader valve. It does not seem likely to me that that plastic hose is intended to hold air at tank pressure. I think the valve below is leaking, or maybe what it connects to on top. Of course, you can take off the hose and pressure test it. If it's just a hose well those are easy to make up.

This is from the factory might not be your pump though:
If air continues to escape through the governor or unloader pressure release valve while operating, this is an indication that the unloader pressure release valve is not closing tightly and may be held open by foreign substance which has lodged on the seat. In order to correct this, remove the governor release valve cap, giving access to unloader pressure release valve spring and ball. Clean thoroughly and return parts in the same order in which they were removed.

I think VR5-8 is the model number for your whole assembled compressor. You might want to look closely at your air pump to find its model number. It might be RV15A, for example. Knowing that number will help you find documents online.

metalmagpie

That valve assembly right below the oil sight glass has a rubber diaphragm in it. Mine started leaking about 10 years ago. I think I bought a kit that had the rubber and maybe a couple of other parts. Seems like the cost was reasonable but I do not remember now. A couple of other parts could leak soapy water will help you find others.

if that is a tank drain I do not know if it does any good. Is there a dip tube inside the tank down to the bottom or is it trying to drain the water only after it gets 6 inches deep?
Bill D

FredC said:

That valve assembly right below the oil sight glass has a rubber diaphragm in it. Mine started leaking about 10 years ago. I think I bought a kit that had the rubber and maybe a couple of other parts. Seems like the cost was reasonable but I do not remember now. A couple of other parts could leak soapy water will help you find others.

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Thanks. I’ll try to find the part number.

There is a manual drain under the tank. I don’t think thats an automatic drain.

Yep, its the automatic drain. THe troubleshooting guide for that part, the ZPT1, says that if the air continues to bleed even if the compressor is not running, then I should check the check valve first.

So this is the check valve assembly.



Any idea on the part number? The one I found for a R15B pump is a 3/4 fitting, but when I measure the threads with a micrometer, they are all 1”. All of the 1” check valves I find have unloaded ports, and mine doesn't.

Or, is 3/4" the inner diameter? That would make since since the most common champion fitting size seems to be 3/4"

car2 said:

hi, a 3/4 npt pipe thread is a bit over 1". Typically, just a basic check valve is required (not a combo check/unloader)since that pump has a centrifugal unloader valve. I don't know if that auto-drain in the plumbing negates/changes the check valve or not. According to a manual for an R15 pump rig, the p/n for the check valve is p05822a; champion or one of the compressor supply places would verify. You might try cleaning the existing one, if the seals/seats look ok. Cheers.

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Thanks. I figured out that the 3/4 is an inner diameter measurement and ordered a new check valve and compression elbow for $31 off Amazon. I wanted to have both just in case. The check valve indicated a plug in the picture, for the unloader port. I just couldn't seem to get a search to return a check valve without the port.

FredC said:

That valve assembly right below the oil sight glass has a rubber diaphragm in it. Mine started leaking about 10 years ago. I think I bought a kit that had the rubber and maybe a couple of other parts. Seems like the cost was reasonable but I do not remember now. A couple of other parts could leak soapy water will help you find others.

Click to expand...

You are correct, sir! Its the drain. Not the diaphragm, though, the valve itself isn’t seating enough to seal. I have ordered the kit.

But, I replaced the check valve anyway, the old one rattled a little.