[rustman]

Hello. I am having trouble with sending units sealing on aluminum intake manifold. Ports on manifold are 1/2" . On one temperature sending unit I used a 1/2" NPT to 3/8" NPT brass reducer. I have it threaded in to the point that no threads are showing. It is seeping very slightly and I am hoping that it will seal itself. On the other fan control sender I got a sender with 1/2" NPT so no reducer there. It is also threaded in to where maybe one thread is showing and it is seeping slightly. The maker of both senders say not to use Teflon tape or thread sealers since this will make for a bad ground and screw up your gauge readings. I am not sure if the manifold threads are tapered or if they should be. I don't think I over tighted the sending unit or reducer and was surprised at how far the reducer and sending unit threaded in so far before they begin to get tight. Any info is appreciated. Thanks.

[joe_padavano]

The manifold threads are almost certainly NPT (tapered). I always use sealer, despite what the instructions say. You will always get a leak if you don't. The act of threading the fitting into the manifold wipes away enough of the teflon tape to get a good electrical contact.

[rustman]

Thanks Joe. I will give it a try.