Hmmm...air leak.

[dhirocz]

So I have an air leak that seems to be driving me nuts.

This is what I know: it leaks down from both the primary and secondary side at the same time. It will leak down fairly quickly (down to 50 psi overnight). It is not audible nor have I found it with the soapy water spray test.

In the last couple days, sitting in the truck while getting unloaded/reloaded, I hear a gurgling sound after the truck has been off for about 20 minutes. Sounds almost like air bubbles in the coolant but it is coming from the driver's dash/firewall area(where the bulkhead for the air lines come in to the cab) Turn the key back on and I went from 120 psi down to 70.

I have recently also heard this walking away or to the truck lately as well. Sounds sort of but not quite like the dryer...which has already been replaced and would have been off anyway.

Since it's not constant, I doubt it is a line itself, probably a leaking valve somewhere in the air system. I'm wondering if maybe air is leaking back towards the compressor...what do you guys think?

[dhirocz]

Well the truck made it obvious. Shut down in N IL for a 34. Pulled out of the fuel island and parked it, then when standing beside it...the cab airbag went from 0 to 60 and blew. At least I got parked on my 34.

Looks like some piece of metal somehow got up there and cut it pretty good. Weren't that old either. That explains part of the problem anyway...

[dhirocz]

Update: new cab airbags helped. Certainly rides better.

Still have a leak. Going to be climbing underneath tomorrow to take a closer look at the supply tank, since I'm loosing out of both tanks when it's shut down.

One thing I notice when I used my tractor air compressor to air offload a split tanker load yesterday...I have a 1/2" fitting with a ball valve on the back of my tractor I hook up a hose to in order to pressurize tanks. Takes awhile, I don't do it often unless I have to. I prefer to pump offload instead.

When I opened the valve coming from my supply tank, the primary tank almost immediately went down to zero...by the time I finished, my secondary dropped down around 70. Since there are supposed to be check valves between the supply tank and the primary and secondary, I'm assuming this is a good indication that these valves are shot?

My understanding here is those valves protect you from loosing air in the primary and secondary tanks if the feed from the compressor or dryer is damaged or you somehow loose the supply side. Would that be a correct statement?

[Shandro]

(10-14-2017 )dhirocz Wrote:  Update: new cab airbags helped. Certainly rides better.

Still have a leak. Going to be climbing underneath tomorrow to take a closer look at the supply tank, since I'm loosing out of both tanks when it's shut down.

One thing I notice when I used my tractor air compressor to air offload a split tanker load yesterday...I have a 1/2" fitting with a ball valve on the back of my tractor I hook up a hose to in order to pressurize tanks. Takes awhile, I don't do it often unless I have to. I prefer to pump offload instead.

When I opened the valve coming from my supply tank, the primary tank almost immediately went down to zero...by the time I finished, my secondary dropped down around 70. Since there are supposed to be check valves between the supply tank and the primary and secondary, I'm assuming this is a good indication that these valves are shot?

My understanding here is those valves protect you from loosing air in the primary and secondary tanks if the feed from the compressor or dryer is damaged or you somehow loose the supply side. Would that be a correct statement?

You are correct there are supposed to be check valves installed. Sounds like either they have failed or maybe they are not even there?

[Rawze]

Also don't rule out that the tanks can get full of carbon and soot from the EGR systems on some trucks. Could be that the tank does not have hardly any more space left inside it.

I have heard of this happening a few times, but never first hand.

[dhirocz]

Possible. I don't think I'm at that point (got that tube feeding the compressor in my intake that blocks off the soot) and that's no longer a concern. I'll be putting my boroscope in the tanks anyway when I swap them out just to be sure.

I did have a failed dryer on it when I got the truck though...the supply tank was full of all sorts of crud that got flushed out. Mostly slurry...

[dhirocz]

So...I put some dye in my air system, ran the truck then checked for leaks. Found it!

...all 13 of them.

Haven't noticed it as audible because it's been leaking slowly from half of the fittings starting at the dryer. I put the dye in after the dryer, and after running for a day she lit up like a Christmas tree. Followed behind with soapy water, some leaked alot and some I really had to soak and wait to notice it bubble. Guess I'll start with a couple check valves on my primary/secondary tanks, order up an air brake fitting kit and start there.

[hhow55]

(10-24-2017 )dhirocz Wrote:  So...I put some dye in my air system, ran the truck then checked for leaks. Found it!

...all 13 of them.

Haven't noticed it as audible because it's been leaking slowly from half of the fittings starting at the dryer. I put the dye in after the dryer, and after running for a day she lit up like a Christmas tree. Followed behind with soapy water, some leaked alot and some I really had to soak and wait to notice it bubble. Guess I'll start with a couple check valves on my primary/secondary tanks, order up an air brake fitting kit and start there.

What dye do you use? And where is it available?

[hhow55]

Did a little searching on the internet.
http://tracerline.com/heavy-duty-leak-detection/