I bought a Yong Heng (I thought) at a yard sale, pretty cheap. It looks like new, no marks on it, oil is clear on the sight glass even. It didn’t have a pump or tubing for cooling, and the temp display is blank. I got all the tubing and a pump, assembled, it runs but doesn’t develop pressure as far as I can tell. The pipe from the 1st stage to the second stage gets hot quickly when it runs. I have seen a video on disassembly but it isn’t clear where the discharge valve is for the first stage. I believe the second stage valves are in the head for the second stage, the videos show one valve under the head in first stage, I think it is the intake. The compressor has both bleed blocks/separators and a discharge moisture filter in the discharge hose, so it seems to be one of the better ones, but it doesn’t say Yong Heng on it anywhere. It appears that it was never assembled or run as there was no seal in the connection for the hose whip, and the Teflon looking seal sticks in there pretty good after it is installed. The moisture filter is pristine, nothing it it or the filter media. I plan to take the cover off and look into the battery situation for the head temp. Any insight to an inspection/trouble shoot would be great.
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Yong Heng troubleshooting
- Thread starter MMCM13
- Start date
FYI THERE WERE 3 OR 4 DEAD ON ARRIVAL BRAND NEW YONG HENG TYPE COMPRESSORS 4SALE WITHIN THE LAST HALF A YEAR THROUGHOUT VARIOUS AIRGUN SITES INCLUDING AGN AND I DOUBT THEY ALL SOLD AND THERES A POSSIBILITY ONE OR MORE MAY HAVE GONE THROUGH A GARAGE SALE.
ABOVE LINK INCLUDES VIDEOS TO REBUILD AND WHERE TO GET PARTS JUST IN CASE.
ABOVE LINK INCLUDES VIDEOS TO REBUILD AND WHERE TO GET PARTS JUST IN CASE.
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Sounds like the 2nd stage valve isn't doing it's job. I'd take the very top off of the 2nd stage and inspect the valve there. If there is any corrosion under it, it could cause it to not seal. The valve is basically just a metal plate with flap that moves out of the way on intake, and covers the hole back up on compression.
Can always check the 1st stage check valve as well. It is a cup and spring on the right side of the head where the first steel line comes out. I had to put a weaker spring in mine due to a scored cylinder (my fault) I polished the cylinder, but still has some low spots so compression isnt quite what it should be. But still works just fine
Can always check the 1st stage check valve as well. It is a cup and spring on the right side of the head where the first steel line comes out. I had to put a weaker spring in mine due to a scored cylinder (my fault) I polished the cylinder, but still has some low spots so compression isnt quite what it should be. But still works just fine
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Maybe a silly question but are you sure it isn't a leak at one of the bleed valves. Some units have two and they can leak.
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It doesn’t seem to leak from the bleed valves, but it doesn’t develop much pressure, so difficult to tell.
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Soapy water solution sprayed on all connections, including the bleed valves, would probably be a good place to start before mechanically tearing into the compressor. Use a dead head in the fill hose or connect to a tank and monitor pressure carefully.
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I've always been able to hear leaks at the fittings. Shut it down, and you will always hear it.
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The cup valve on 1st stage was worn, I cleaned the valve seat out and was surprised to see a spare in a bag of parts. Then the second stage inlet valve was all covered with black carbon residue. It has a flat washer for an inlet valve (spare in the bag for that too). The outlet valve was dirty, but not like the inlet. This is an oddball, the discharge valve is combined with the blow out disc on the top of the head. The oil sump was overfilled by quite a bit, I dumped oil till it was back down in the sightglass. I ran it and it built pressure to 2500 PSI, but the filter housing outlet fitting has no bond-seal or gasket, so it leaks, a lot. The hose fitting there is corroded, so I am going to see about a replacement filter and hose assembly. Popped 2 batteries in the thermometer and that works now. Hoping to find a kit with filter, two hoses and a foster fitting for fill. A few spare filters/media would be good too.
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When you rebuild, here's the only video I found on the reed valve and how to re-assemble:
https://www.youtube.com/watch?v=24sGXYkd4NY
https://www.youtube.com/watch?v=24sGXYkd4NY
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The clone compressor has a different head and the intake and discharge valve is set up different. The head in that respect is easier to service than the one in the video. The discharge valve is in a fitting in the top of the head, the tubes are on each side of the head.
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