Leak in scott air tank second set of gages

I fill to 4500psi and dunk the whole tank in a bath tub.

Clean water of course.

Go to a welding supply outfit & buy some of there leak testing liquid it will show it, about 7 to 8 bucks . Best of luck D.

Doubtful you got 2 leaky gauges imo. but its possible.

Best leak detector liquid, is soap suds. Dawn detergent few drops in cup of warm water, frothed up with your fingers beating it to a sudsy foamy froth. Grab a handful of froth and apply (completely, thickly, cover area with suds froth) to suspected area. It will bubble up wherever there is a leak, even a small leak is easily seen in the suds within seconds....

But, what O posted above is your best bet if you don't know what area the leak is in. Submerge a full tank in tub and look for bubbles to pinpoint your leak, best way for sure if you have no idea where the leak is.

jmo

WARNING. If you dunk your tank you likely will have a cloudy pressure gauge afterwards. The moisture seeps in and clouds the gauge but rarely dries out afterwards. It's like the face of a cheap wrist watch that gets wet and is cloudy.

The soapy water test will show where the leak is. There is a fine line between wrench tight and loose enough for the neck o-ring not sealing. One time in the past I hand tightened my tank valve only to discover a leak because it wasn't snug enough. Either that or you aren't using the correct sized o-ring in the valve neck. A tank valve area leak should be very easy to locate where it's coming from.

Looks you you've got the same valve I had. Mine started leaking pretty good. I got a bisley valve from bestfittings that should be almost here. 

If the gauge gets moisture inside that's no problem at all and super easy instruction on how to fix that and also recalibrate gauge-manometer videos I posted few days ago.

You are Actually dunking it in the bath tub to see if the tank itself has a crack in it since you mentioned trying TWO different setups. Which is what I hope is not the case that would render the tank unsafe to use.

You could put a balloon or a condom (clean one of course) or a disposable latex rubber glove over the gauge with couple wounds of rubber band too... Before bath tubbing it.

OH-DUH? Try putting a large latex rubber glove with ziptie or rubber bands over that whole assembly...