Cant find leak

So, Im about to rip all my horn crap off my truck and set it on fire.
Ive got a triple set of small horns on my truck. They are mounted behind my front bumper. Ive got a hornblasters valve mounted under the passenger side door and a 7 gallon tank under the bed, no compressor.
The horns came with a cheap solenoid when I purchased them about a year ago. The solenoid that came with them didnt work so I got a replacement. It worked great and there was no leak in the system for 8 months, then that solenoid quit working. I bought another solenoid just like it and while replacing it, I also changed the gauge on my tank, the fittings, etc. Ever since, Ive had a slow leak, about 10 psi every 24 hours. Ive coated EVERYTHING in liquid soap but can not find the leak. I went from the slip-in hose fittings to the kind that use a little crimp ring and are threaded tight. There was still a leak after that.
I figured the tank gauge was leaking so I changed that but it still leaked.
After than I knew it had to be the solenoid valve leaking. I bought a more expensive valve from hornblasters and after I installed it, there was still a leak.
Yesterday, I bought a new, more expensive air hose (not the thin plastic hose like my old setup), all new fittings, new gauge, new manifold and even used a different tank, and its STILL leaking!
Ive replaced everything that could possibly be an issue. Ive been using about 2 wraps of teflon tape on all the threads. Should I use more? Should I put on enough of it so that the fittings get tight before threading all the way in? What am I doing wrong?
Here is the tank setup. On the other end, the hose threads into an adapter which threads into the solenoid valve.

Welcome to the forums.
Teflon isn’t the best, but if you checked with soapy water then that’s kind of irrelevant.
If they don’t leak - they don’t leak.

I would say it’s your check valve, but you probably don’t have one.

Use soapy water on the whole tank. Pay attention the welds. Heck if I’d gone through all that - I would have submerged the whole friggin thing in a bathtub.

Even with such a slow leak, I should still be able to see bubbles with everything coated in liquid soap, right?
I must just be missing them somehow. What is a better thread sealer than teflon tape, thread locker?

BTW, the packaging with the solenoid valve said operating pressure is 150-250psi.

I have not put more than 115psi in my tank. Could low air pressure cause the valve to leak?

loctite 545… Use it once, you wont even think about using teflon tape again!

^^Yeah gotta pick me up a bottle for my redo this year.

Hey nissan11 - when you say liquid soap, are you diluting it with water or using it straight? You want it to be super runny - basically soapy water. Think of stuff kids blow bubbles with.

buy it online… ebay has best prices when i looked last.

i needed it that day and ddint realize it was a specialty item and ended up paying $50 for a bottle at grainger. RIP OFF, but i took a vacation to install my horns and needed it that day.

Will definitely buy online - haha like everything else. Been shopping around.
Not a ton of places carry the stuff, but Amazon is my goto place.

Makes me wonder if the Permatex copy is as good, but I’ll get the Loctite anyway.

Any good teflon based pipe dope will work as well as Loctite. Our mechanic uses “LA-CO Slic-tite”.

I’ve been using pure dawn, but I just tried again with it diluted and I still can’t find any bubbles. I turned off the supply valve on the tank and it’s still leaking, so that eliminates the hose and solenoid valve. I can’t see one bubble anywhere on the fittings or manifold, and this is the second tank I’ve tried. Any other ideas? Should I really just submerge it in the tub? Will 1 psi per hour leak be noticeable under water?

Yeah straight soap is waaay too thick. You need water with a little soap in it.

If you are at your wits end and have no other options - dunk it.
It sounds extreme but what else can a guy do?
The bubbles should be easy to see even for a slow leak.

I’m filling the tub…

In the picture I posted, isn’t the manifold setup correctly? I assume the shut off valve closes the port directly across from it, not the port below it and to the side. With the valve off, I began unscrewing the hose from the manifold and air began leaking. It turns out, the line, and therefore the solenoid valve HAVE been under pressure, so the leak isn’t narrowed down to the tank. Where I have the gauge, is that where the hose is supposed to be connected? This doesn’t make sense to me, my old manifold was setup the same way and the valve shut off the air supply to the hose. Do I just have a bad valve at the tank?

take a spray bottle and put a squirt or 2 of dish soap in there… shake it up and spray on fittings. If it is leaking air you will see tiny bubbles.

When u said your filling the tub, are u putting fittings in there? if so i hope you have them pressurized… otherwise all your doing is washing them :wink:

Yeah I was going to remove the hose and submerge the tank, manifold and gauge with 100psi in the tank, but I discovered the shut off valve isn’t working so I can’t remove the hose without losing all the pressure.

LOL yeah I hope it was understood to have the tank pressurized!
I am not familiar with that valve / manifold in the picture.

Silvy is right though. Spray with soapy water and you will see tiny bubbles.
Spray the heck out of it!

No need to . Just use spray bottle with some soap, shake up and spray on … look for bubbles. easy as that. Get some loctite 545 and be done with it.

I bought some hardware today that will allow me to eliminate the gauge and supply valve. Also yellow Teflon.

I can’t get the yellow Teflon to stick to the threads. It’s a lot thicker than white Teflon so how many wraps was I supposed to make? Because I wasn’t sure about the tape, I bought some permatex high temp thread sealer and after letting the air out of the tank, I applied it to the fittings and tightened them. The instructions aren’t very detailed, but I believe I am supposed to let it dry for 4 hours before putting air back in the lines?

I disconnected the hose at the horns and put it under water. There were no bubbles, so the valve must be good. I put liquid soap on everything else and did find a leak from the new schrader valve, where it threads into the new manifold. I fixed that leak, and could not find one anywhere else, with repeadedly spraying soapy water everywhere.
The system is still losing air pressure and I dont know what else to do.