Radiator Temp Sensor

[Steve Sherman]

I just put in a new radiator (old one had the hose nipple break off).
 In the process I reused the temp sensor that screws in  under the lower
rad hose; it was only a few months old and working fine.  The problem I
am having is that there is a slow seeping type of leak coming from that
sensor on the new rad.  (FWIW it sealed just fine on the old rad).

When I moved it over, I reused the copper crush washer under it. I did
not torque it as much as I might, because unlike the old rad which had a
brass insert for the threads on this sensor, the new rad (AKG) seemed to
be all plastic threads.  Seems that one could install the sensor without
a washer, or even with a thin layer of RTV, although those options
require draining the rad again...

My questions are:  Does anyone know if AKG does have a brass insert for
the threads on their Audi radiators (eg is it safe to just torque this
some more)? And any suggestions on the best / easiest way to top this
slow leak from around this sensor?

TIA