Jaguar Repair: SU auxiliary enrichment device, air fuel mixture, thermo carb

Question
I have a 1966 Jaguer 3.7S with 2 HD-6 carburetors.  The choke is comprised by a third smaller carburetor called an Auxiliary Enrichment Device or Thermo Carb.  The car starts well from cold but the Auxiliary carb makes a very loud hissing sound for about 15 seconds then it stops hissing and gas starts pouring out of it.  I know that the solenoid energizes properly when cold but could the fuel pouring out be because it doesn't reset when the engine is warm?  Also why does it make such a loud hissing sound?  My understanding is that it will hiss but relatively quietly.  Please help me!!!    Thank you so much

Answer
Hi Roger,
When the solenoid is activated it lifts the flat valve off it's seat allowing air to travel through the "Third Carburetor" (choke system)
This also pulls the needle down on to it's adjusting nut (next to the solenoid)
The hissing noise is the air going through the small tube supplying a rich air/fuel mixture to the intake manifold.
Part of this third carburetor shares the float fuel and level of the carburetor that it is attached to. So all joints need to be sealed or it will leak. Another reason excess fuel could be in the area is if that carburetor float is flooding or the float level is set too high.
The hiss is not quiet when the hood is up. Every one I worked on were very noisy especially with the hood up and even more so if the air filter is not in place.
Howard