I just tested the temperature sending unit on my '83 F150 5.0 L and it appears to be bad, so I ordered a new Motorcraft sending unit. I've read conflicting advise about wrapping the threads in teflon tape. It looks like they come with some kind of treatment on the threads already. How do you all do it?

 

Use what they have, don't add any. You simply need a good ground connection to the body of the sender. So try not to interfere with that if you can help it. You can take a ohmmeter and check it after you install it by putting one lead on the body of the sending unit, and the other lead on the engine block.

 

That red dry paste is thread sealer. Just thread it in as is.

If you do have to apply thread sealer on any sensor avoid teflon tape and pick up thread sealer paste such as ARP`s thread sealer which is a semi gritty feeling paste that you put a thin layer on the threads it will seal but will not prevent the sensor from grounding.

Like wise never under no circumstance use teflon tape on fittings that is used for the fuel system.