I installed an aftermarket guage kit on my 89 stang, and worked fine for a while, but now there is a leak where the copper line is screwed into the block, I tightened it as much as possible but still leaks.. I had heard you could'nt use thread tape but don't know what else to try!
I believe it was on the vdo website, said it would mess with pressure reading, but I did'nt want go through the trouble of putting it on, if that was the case!...I will try it and see if that cures it ..Thanks!
If the thread dope is only applied to the threads (Like Skip, I dont apply it to the top couple threads) and wrapped the correct direction, I dont see how it could cause an issue with regard to blocking the flow of oil, etc.
Pipe threads often need some sort of a means of sealing - and even then I still sometimes get a leak.
I used a liquid thread sealer on mine. It comes in a little white tube and is about the consitency of tooth paste. You just put a dab on the threads before you tighten it down and it sets up and seals the connection. Also you say you go it as tight as possible, it is really easy to overtighten those connections and that can cause a leak as well.