Question about my air valves and stuff - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jimmydean · 01-05-2007, 10:45 PM

So the dump valve is normally closed. So if I add air to the bag, there is air in the line between the dump valve and the bag, right?

So why is it when I open the drain on my tank do I lose air in all my bags? If I understand how the system should work, the inly time the air should leave the bag is when the dump valve is open.

All I want to do is fix the leak in the left rear valve setup. But I have to put the whole truck on stands because when I drain the tank, I lose preasure in everything. Is that right?

*Shane* · 01-05-2007, 11:08 PM

I believe, but don't hold my feet to the fire, the reason is because the valves use the residual pressure in the lines/tank to keep the valve closed.

Once energized, it will open ... but if there is no pressure in the lines/tank, then there is nothing there to keep it closed and then the "back pressure" in the bag will force the valve open.

entourageguy · 01-05-2007, 11:40 PM

you should be able to put a one way valve in there somewhere to stop that.
Brian ..

jimmydean · 01-06-2007, 12:12 AM

Shane, that makes a lot of sense. That's sort of what I was thinking, so that leads me into another question. How much back pressure is needed to keep the valve closed?

I think I have all my tank leaks fixed. Right now my passenger side holds air for at least 24 hours. The driver front loses air in about 8 hours, the driver rear loses air in about an hour. I am pulling it apart for the third time tomorrow once I shoot it with bubbles and see where it's leaking this time.

If I had an engine driven compressor, the leakage wouldn't bug me as much.

PBFAB.COM · 01-06-2007, 12:15 AM

Shane is correct. The majority of valves will use the pressure in the tank to keep them closed. If the pressure in the tank is less than the pressure in the bag and line, the valve will allow the pressure to 'equalize'... all the way down to 0psi. Doesn't seem right... but that's how it is.

67Fleet · 01-06-2007, 11:11 AM

You can put a check valve in between your line from the bags to the tank.

jimmydean · 01-06-2007, 01:16 PM

Man, I can't find a spot for my water trap, where the heck am I going to put a check valve too?

The good news is the front seems to be holding air now. I had 70 psi in the 3 bags yesterday at 5:00 and this morning there was still the full 70. If this latest "fix" works, I might have a somewhat leak-proof system!

lost wages · 01-06-2007, 08:17 PM

i had the same questions on my truck, i cut a line to redo some things and the whole truck layed out, i thought wtf? seems to me they should hold air if something were to fail while your driving. guess ill get to work on some bump stops just in case.

droppedgmc · 01-07-2007, 12:40 AM

go to www.*****************. they have the check valves. air valves have to have a constant preasure on them. when the psi in the tanks get low, it'll make your truck drop

01-05-2007, 10:45 PM	#1
jimmydean Registered User Join Date: May 2005 Location: Beaverton, OR Posts: 3,728	Question about my air valves and stuff So the dump valve is normally closed. So if I add air to the bag, there is air in the line between the dump valve and the bag, right? So why is it when I open the drain on my tank do I lose air in all my bags? If I understand how the system should work, the inly time the air should leave the bag is when the dump valve is open. All I want to do is fix the leak in the left rear valve setup. But I have to put the whole truck on stands because when I drain the tank, I lose preasure in everything. Is that right?

01-05-2007, 11:08 PM	#2
Shane Account Suspended Join Date: Jun 2000 Location: over yonder Posts: 14,270	Re: Question about my air valves and stuff I believe, but don't hold my feet to the fire, the reason is because the valves use the residual pressure in the lines/tank to keep the valve closed. Once energized, it will open ... but if there is no pressure in the lines/tank, then there is nothing there to keep it closed and then the "back pressure" in the bag will force the valve open. Last edited by Shane; 01-05-2007 at 11:09 PM.

01-05-2007, 11:40 PM	#3
entourageguy Yellow truck club Join Date: Apr 2006 Location: Barrie Ontario Posts: 2,080	Re: Question about my air valves and stuff you should be able to put a one way valve in there somewhere to stop that. Brian .. __________________ ................................................................ Brian ...... My hub garage address http://www.hubgarage.com/mygarage/59apache I gue$$ everything has it'$ price ALL GONE NOW *59 Chev Apache* *PRAISE THE LOWERED* 350 700r lokar shifter power MII front end, shockwaves tilt, 4 wheel discs 4-link and bags 10 bolt limited

01-06-2007, 12:12 AM	#4
jimmydean Registered User Join Date: May 2005 Location: Beaverton, OR Posts: 3,728	Re: Question about my air valves and stuff Shane, that makes a lot of sense. That's sort of what I was thinking, so that leads me into another question. How much back pressure is needed to keep the valve closed? I think I have all my tank leaks fixed. Right now my passenger side holds air for at least 24 hours. The driver front loses air in about 8 hours, the driver rear loses air in about an hour. I am pulling it apart for the third time tomorrow once I shoot it with bubbles and see where it's leaking this time. If I had an engine driven compressor, the leakage wouldn't bug me as much.

01-06-2007, 12:15 AM	#5
PBFAB.COM Senior Member Join Date: Dec 2003 Location: Mesa,Az Posts: 3,981	Re: Question about my air valves and stuff Shane is correct. The majority of valves will use the pressure in the tank to keep them closed. If the pressure in the tank is less than the pressure in the bag and line, the valve will allow the pressure to 'equalize'... all the way down to 0psi. Doesn't seem right... but that's how it is. __________________ www.PorterbuiltFabrication.com Phone: 480-297-2621 E-mail: sales@pbfab.com Find us on FaceBook under Porterbuilt Fabrication Specializing in Chassis and Suspension Components for your Classic Chevrolet Truck. We offer components from the following manufacturers: Porterbuilt Accuair Ridetech (Air Ride Technologies) Air Lift Wilwood Intro Unisteer ECE Gotta Show Air Lift Borgeson CPP Supporting this forum since 2003!

01-06-2007, 11:11 AM	#6
67Fleet Outlandish Trends - FL Join Date: Jul 2005 Location: Orlando Posts: 1,396	Re: Question about my air valves and stuff You can put a check valve in between your line from the bags to the tank. __________________ -Bret 67 short-fleet sold!

01-06-2007, 01:16 PM	#7
jimmydean Registered User Join Date: May 2005 Location: Beaverton, OR Posts: 3,728	Re: Question about my air valves and stuff Man, I can't find a spot for my water trap, where the heck am I going to put a check valve too? The good news is the front seems to be holding air now. I had 70 psi in the 3 bags yesterday at 5:00 and this morning there was still the full 70. If this latest "fix" works, I might have a somewhat leak-proof system!

01-06-2007, 08:17 PM	#8
lost wages Registered User Join Date: Apr 2001 Location: jefferson city, mo Posts: 1,364	Re: Question about my air valves and stuff i had the same questions on my truck, i cut a line to redo some things and the whole truck layed out, i thought wtf? seems to me they should hold air if something were to fail while your driving. guess ill get to work on some bump stops just in case.

01-07-2007, 12:40 AM	#9
droppedgmc Truck Enthusiast Join Date: Dec 2006 Location: Arlington, WA Posts: 1,346	Re: Question about my air valves and stuff go to www.*****************. they have the check valves. air valves have to have a constant preasure on them. when the psi in the tanks get low, it'll make your truck drop __________________ '85 swb



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