I got the pressure switch replaced and it took care of that leak from the diaphragm but now I have a new one. It’s a slow hissing leak coming from the base of the input line to the tank. Seems to be just a pinhole sized leak right where the fitting screws in to the tank and I can feel a slight stream of air. When I brush on some soapy water it actually looks like it is sucking the water in rather than blowing it.
Compressor
top view
If you look at the pictures above it is at the base of the fitting which you see right over the gauge on the right of the tank. The pressure relief line exits from the back side of that fitting. Is that fitting with both the large input line and small relief tube a special one way valve of some sort or what? I would like to know what is what before I start taking things apart to try and fix the leak. Do I maybe need to just unscrew that fitting and put on some fresh thread sealer or tape and then screw it back in to stop the leak? Would appreciate some help. Thanks
Mark

 

yes that is the check valve for the tank, make sure it is not bleeding back thru to the compressor. you should be able to pull the unloader line(small) off after the compressor stops and relieves pressure. disconnect power before loosening lines and drain tank of all pressure before pulling check valve.

 

How do I test the check valve after removing or determine if it is leaking back in to the pump? I think it's just leaking out from right where it threads in to the tank. Do you think just replacing it with something on the threads may clear up the problem and what should teflon tape, pipe dope or what be used on the threads? Thanks for the help and sorry for all the questions.
Mark

 

there is no way to check after the valve is removed, when you pull the unloader air line(small line) off the check(with pressure in tank) you should not get any air back thru that opening, meaning air is beading back thru to the compressor. another way to tell is if your breaker trips on start-up. possibly the belts may slip/motor will not want to start instantly.
no problem about the all questions, thats what the board is for.

 

Yep, thats the discharge check valve and it appears to be 3/4' X 1/2' pipe threads. If it is leaking you would hear air leaking from the bleed valve on the side of the pressure switch. The check valve is made of brass and pretty tough. Go ahead and relieve all the pressure from the tank amd remove the check valve, put some pipe dope on it and re-install it. Stay away from teflon tape and use some lock-tight thread sealer to seal it. Good luck

 

Thanks a lot for the tips guys. You've been a lot of help. I'll go get a bigger wrench tomorrow and try resealing it.

 

I would make certain that it wasn't the tank-- Ac make great bombs when they explode due to a malfunction such as a pin hole created by defect and if you have ever seen someone injuired and they live-- you will be amazed. IF it is the tank either scrap it or have it welded by a certified pressure tested welder-- these are simply not something worth your life.

 

Well I removed the check valve and the threads on the valve and the tank are clean, straight and no rust. I cleaned everything up and applied some fresh pipe compound before screwing it back in. When I pump up the tank it is still leaking from the same spot. I can feel a pinhole stream of air as I move my finger or a piece of paper over the area but I could swear when I brush on soapy water it appears to be sucking it in to the hole... Is that possible?? It's right where the threads contact the tank at the base of the weld. Red arrow points to the spot in this pic.
So what next? I have no idea where to go from here.
Mark

 

Looks like you did a good job of repairing the valve. I cannot see why it should be leaking but from the amount pipe dope evident it shouldn't be coming up the threads. Maybe the check valve itself is fractured or possably eroded from the inside. Maybe also like Ghostgunn said look at the tank closly. Get some Mr. Bubbles from your kid, drain the tank down to around 75 PSIG ant check it again. It may be that at full pressure the leak is large enough to blow the leak solution away and give the appearence of sucking it in. I have experienced that in the past.

 

Fixenair, would you agree that the check valve is bad? I had the same problem once and replaced valve with a new one from Napa for around $40.
Is there a better place to get one?

 

Used some blow-bubbles with the wand from my son's stash to narrow down the leak. It is coming out from where the edge of the threads contact the tank. The threads tapped in to the tank as well as the threads on the valve looked good but I guess they could still not be making tight enough contact? I did have it screwed in as tight as it would go. Going on that, does a new check valve still sound like my next step?
Thanks a lot!
Mark

 

How tight should I torque that valve? I could probably get tighter with a lot of force but was afraid I might strip the threads or crack the tank...

 

Because the threads are tapered you would have a tough time stripping the threads. You could though split the Bonney fitting in the tank or collapse the check valve. You would have to try real hard though. Use a 14" pipe wrench and pull as hard as you can, should be tight enough. If you are using Lock Tight pipe dope you could get by with a lot less torque. I have assembled 3000 psig Nat. Gas systems hand tight and had no leaks using Lock Tight pipe dope.

 

Well that worked. I pulled a lot harder than I ever thought I would need to, but no more leak. Had to get new copper pipe and re-plumb the release line. Actually screwed up two 5' lengths trying to get the bends right and everything to fit but was worth it. Picked up a cheapie Northern Hydraulics air tool set for $99 this morning and also got a pressurized sandblaster. Came with an impact wrench, drill, grinder, air hammer, and DA Sander. I usually don't buy low-end tools but for the price I won't cry when they fail. DA Sander is working great on the tailgate.
Thanks all for the help.

 

Great! Glad you got it fixed and it wasn't the tank. Aren't air tools great? I use air for all my tools. Impact, ratchet wrench, saws, drills 1/4' & 1/2", gasket scraper, DA Sander, Air chisel and I even have a small air powered air conditioner. Blows cold air, cool huh. Have fun with yours!