Mystery Leak?

The install on my daily beater is a little more extensive than the average train horn setup.

I’m running a K3 with the #2 and #4A bells facing down in each front fender well and the #1 bell facing forward under the rear using individual manifold mounts.

Each bell is fed by their own individual 3/8" solenoid (HornBlaster) as well as a drain solenoid for the 3 gallon aluminum tank that fires through the grille.

A 200psi Airmaxxx Compressor is hidden under the hood behind the front bumper.

I plumbed everything with 3/8" air brake tubing and brass compression fittings.

More parts = more chances for possible leaks

Been over the entire system a dozen times on my lift with soapy water and found absolutely zero leaks.

I’ve had the car sit for several days at a time without use and pressure fluctuated up and down normally a few psi with ambient temps.

That is, however, only when above freezing.

Once the temp drops below freezing, the pressure of the system routinely drops (about 5-15psi per hour) and will continue to drop until the system is empty :frowning:

Tried spraying soapy water over the visible lines and connections under the hood, but that only turned to ice as fast as I could spray it lol

On the lift at my shop spraying the rest of the system from underneath, I don’t see any bubbles, but then again, the shop is heated.

I figured the check valve on the leader hose is probably back feeding, but I don’t see any bubbles when I put the intake line in a bottle of water.

Furthermore, I have a ball valve between the leader hose and the tank (for testing purposes), so after filling the tank, I’m able to lock out the compressor completely.

Still, after a night in freezing temps, the system is nearly empty by morning :confused:

The system still works as it should, but just has to refill way more often.

With my old compressor (ViAir 450c), I had a similar issue, but it was clearly the check valve back feeding (would fail bubble test back feeding into the intake line).

A quick fix was to pour some warm water on the check valve.

Tried that with the new compressor, but the problem still persists.

Again, once the temps are above freezing, the system is perfect and leak free, but once I see ~32* show up on the weather channel, it’s like it’s almost expected that my tank will be empty :rolleyes:

Any suggestions?

I’d look at the check valve again, possibly back feeding internally into the compressor. You wouldn’t get any bubbles this way and would still have a leak.

Things are a bit off once the temps drop … I get that here in Idaho (Pacific Northwest) as well.


With my old ViAir 450c, whever the check valve would leak, it would back feed into the compressor and show up with a bubble test (stick the intake line in a bottle of water)

With the AirMaxxx compressor, the check valve is much bigger and doesn’t show any signs of leakage using this test.

Furthermore, I have a ball valve between the check valve and the tank, so I can lock it off completely, yet it still loses pressure when it drops below freezing.

Try Disconnecting the Horns from the solenoids, one of them could be leaking.

Sounds like you might have what we call “winter leak” in the HVAC business. With mechanical type connections and below freezing temps some fittings might contract just enough to cause a leak.