Used thread sealant when installing a new temperature sending unit

[JCamp]

This is my first time through some simple mechanical projects on my MEP802A genset. Before I understood something about how ohms and resistance work, I had the idea to put thread sealant on the threads on my water temperature sensor sending unit. Now it’s probably not grounding properly, I’m getting lower temperature readings than I should. My challenge now is how do I clean it out nicely from the engine bloc side? Any suggestions on how to get rid of thread sealant inside the threads? Could I spray brake cleaner? Just carefully clean with a rag? Any ideas?

 

[2Pbfeet]

This is my first time through some simple mechanical projects on my MEP802A genset. Before I understood something about how ohms and resistance work, I had the idea to put thread sealant on the threads on my water temperature sensor sending unit. Now it’s probably not grounding properly, I’m getting lower temperature readings than I should. My challenge now is how do I clean it out nicely from the engine bloc side? Any suggestions on how to get rid of thread sealant inside the threads? Could I spray brake cleaner? Just carefully clean with a rag? Any ideas?

I guess that my #1 question is:

What kind of thread sealant did you use?​

In general, yes, a rag can work ok, but it depends a bit on what you sealant used. My goal is always not to push any thread sealant or remains of thread sealant into the coolant area. If it is something like, say PTFE (Teflon) tape, I would use some very fine tweezers. When you are done, you can carefully thread a very narrow air line in, being careful not to touch the threads and blow out particles, but again that depends on what you used initially. Some non-hardening thread sealants are going to take some very fine bristle brushes and cotton applicators with a drop or two of solvent. (E.g. "Monster" sealants that seem to go everywhere, though they are great sealants).

These are a 1/8 NPT tapered thread in brass and should be self sealing against the block.

All the best,

2Pbfeet

 

[Guyfang]

Start the set. Let it get to its operating temp. Look at the reading. Take a wire and clamp one end to a bolt/Ground point. Have someone touch the wire to the temp sending unit, while you look at the meter. Any change? In not, maybe there other reasons? Maybe you are over thinking the problem? TEST, TEST, TEST. Always test and not guess.

 

[rickf]

Thread sealant does not usually present a problem wit pipe threads, they get tighter the more you thread them in and the thread will cut through the sealant. You can check with an ohm meter to see if you have a good ground. Just go from the metal body of the sender to a clean spot on the engine and see if you have a measurable resistance. Most military senders have a closed circuit sender where the power and ground are wired in. If it has two wires that is what you have, if it only has one wire then it uses the threads for ground.

 

[Ray70]

I use thread sealer on all NPT threads including engine sensors and never had an issue with grounding.
Usually when you remove the sensor you'll find that probably 90%+ of the sealer was pushed up the threads and hardly anything is left in the threads themselves. The threads will cut right through and ground the sensor just fine, no matter what you use for sealant or tape.