91 ranger 4.0 ohv
I removed the water temperature sender (1 wire sender) and the Engine coolant temperature sender (2 wire plug) from the lower intake manifold to clean the manifold while I am doing a valve job. What kind of sealant should I use on the threads while replacing them. I know for the one wire sender it reads the variable ground between the threads of the sender and the one wire. The two wire sender I am not sure if the threads need to be grounded. I am thinking the sealant needs to be able to be conductive as well as seal well and high temperature. I thought of using teflon tape or paste or permatex high temp thread sealant but does not seem like it is conductive. Anyone know what to use.

I have a Ford manual and this is what it reads:
Use D8AZ-19554-A (esg-m4g 194-a, esr-m18p7-a)
Pipe sealant with teflon or equivalent or small amount of electrically conductive sealer.

 

I used teflon tape on the single connector sending unit on a 2.3 lima. The teflon tape will get 'cut' by the threads in most cases and make a metal-to-metal contact enough to get a decent ground. I would think it usable on both sending units.
You can check that you have a grounded sensor outer by using a VOM to measure resistance to the bare block. It should be minimal. I did not do that when I replaced the sender, but was pretty sure it grounded given what teflon tape looks like when disassembled on all other plumbing I have done.
tom

 

Loctite makes a liquid pipe thread sealant that yields where the threads touch, to make good electrical contact on sensors that need a good ground. I've used Loctite PST 565 anaerobic (cures in the absence of air) pipe sealant for years on oil & temp sensors. You can get it in a small 0.2 fl/oz counter mans size p/n 56507, for small jobs.

 

I use tape or liquid all the time no issues. It is really more of lubricant allowing easier and deeper seating of the tapered threads