Temp. sending unit leaking

I installed a new 440 Source aluminum water pump housing on my 440 with a new aftermarket temperature sending unit. The sending unit leaked through the threads. I replaced the new sensor with my old stock unit and it also leaks. The leak is very small but it's still a leak. Can I put anything on the sending unit threads such as teflon tape or teflon paste (pipe dope) or will a sealant block the sensor's ground? Would a small rubber o ring work?
Thanks for any help.

try a bit of permatex brown usually works

Tape or dope is fine. Use both sparingly. Never a problem here, both iron and aluminum intakes...

Permatex Pipe Sealant

You won't have a leak with this material. Just don't tighten it excessively or you probably won't get it out. Just a comment, the concern about insulating the sensor is misplaced, Pipe threads are tapered so the thread flanks will always have metal/metal contact. Thread sealant does nothing but fill the voids in the threads.

High temp silicone on threads. let it cure overnight

I have teflon tape near the top of the threads.

I agree.

The teflon tape & pipe dope fills the gaps in the threads but when you tighten the sensor down you will get metal to metal contact through much of the threads.

My stock temp gauge didn’t work at first with a new sensor that had PTFE tape on the threads, tightened it more and now it works

Perfect application for Never-Seez.

You installed a sensor into Aluminum & didn't use anything on the threads??

Teflon tape or paste on NPT threads - always.

i use loctite 567 paste for everything.
works with gasoline, oils, natural gas, propane, butane, potable water, water tanks, and any type of antifreeze.
good for any type of fittings as well.
been using this stuff for 40 years or so, and i really like it.

That's the Loctite equivalent of the Permatex 59214 I use. Good stuff whichever you choose.

Thanks for the replies. I used the high temp silicone that I have.

No I didn't. I assumed, incorrectly, that sealant on the threads would impede the grounding between the sensor and the housing. Now I know better.

having to repair many threaded connections over the years where dis-similar materials were used, it doesn't take long to learn about anti-seize and sealants.
and stainless threaded connections are "fun" unto themselves.

Stainless steel thumb screws into aluminum rods at a seacoast
led me to create many new curse words.

I also made the mistake of assuming Dielectric Grease would hurt electrical connections
because I had been lectured over and over that
“Grounding connections to divert lightning strikes to Earth ground must be kept totally free of paint or visible corrosion”

Same basic approach. I've had people tell me not to use dielectric grease on light bulbs "because it insulates the bulb". No, you still have electrical continuity at the mechanical contact points. The grease just fills the voids to prevent corrosion.

Brass fittings seem to be the cure when used in aluminum. Have always been able to easily remove the brass ones from my swap meet intake buys while the steel fittings give me giant headaches.