Finding Stubborn Small Air Leaks

[tehfrr]

Any advice on how to find a small air leak?
Ive tried soapy water, an incense stick, dry ice, and a $50 Chinese ultrasonic leak detector.
None of the above have been able to find the leak.

When I pressurize the system and plug in a digital pressure gauge, I still see the pressure slowly dropping.
There's a check valve installed so the air shouldn't be going back into the compressor.

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[roaniecowpony]

It may be backflowing thru the compressor?

 

[IanNubbit]

Small air leak where? In the cab? The compressor??

 

[ParadigmDawg]

Is the compressor kicking back on when pressurized?

 

[tehfrr]

It should not be backflowing through the compressor, I am using a one way check valve (#4 in the pic below)

The leak is somewhere between #4 and #12

Yes it will kick back on after a couple hours. What I do verify is attach a digital pressure gauge to #12 in the photo. Its slow but you can see the pressure going down.

 

[bjm00se]

Kicks back on "after a couple of hours?" That is one tiny leak. Your expectations may be too high.

Also, you have an awful lot of faith in that backflow preventer valve. Seems to me that it's just as likely to be bleeding this miniuscule amount of air as anything else you've shown us in the system.

 

[tehfrr]

Kicks back on "after a couple of hours?" That is one tiny leak. Your expectations may be too high.

I agree its one tiny leak. I want it done right before I install it under the seat though so I dont have to peel it all apart later.. Do big trucks tolerate small leaks in their brake lines?

 

[bjm00se]

Do big trucks tolerate small leaks in their brake lines?

I don't actually know the answer to that question. Certainly *large* leaks would be a safety issue. But they're using brakes all the time, and so the compressor is cycling on and off all the time with use to keep pressure up. It's not obvious to me that they'd have entirely perfectly leak free systems. And given the usage environment, that actually seems kinda unlikely.

But never having worked in trucking, I admit that I'm idly speculating here.

The fact that the compressor has to cycle on occasionally is exactly why I don't have my compressor mounted in the cabin of my jeep.

 

[ParadigmDawg]

I think most would be happy if it kicks on in a couple of hours. You can air up 24 tires in 2 hours.

Mine may leak after a certain amount of time but it holds for the 10 minutes that I tested it which is plenty good enough for me.

 

[azjl#3]

I would isolate pump and all the valves first, verify that whole system does not leak back.

I have a HF pressure gauge looks like yours, i know that leaks a little, and I know quick disconnect fittings leak.

 

[tehfrr]

I did not consider the possibility of the gauge leaking.

I get it that tires are quick and done but I intend to install other components that would use compressed air. Some I assume very little, others not so much.

I don’t have a storage tank installed yet, but my goal is if I filled a 2 gallon tank up to 150 PSI, I could leave it sit and come back a week later and it’s still at 130 or better. Is that an unrealistic expectation?

 

[wibornz]

Personally, I think you are putting in to much effort. Turn on the compressor when you need it, turn it off when you don't.

 

[JL ME]

Dawn dish soap and water in a spray bottle works every time for finding leaks.

 

[58Willys]

. Do big trucks tolerate small leaks in their brake lines?

Yes. Shut off a tractor trailer rig and come back two days later, it will not have any air pressure.

 

[PatriotX]

My large garage compressor will hold pressure for a few days, unless something is attached to the quick-connect chuck.

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