I’ve got my brass (pretty sure they’re brass) temp senders off the water rail, which of course is aluminum. Some of them had some greenish/bluish discoloring, as I know brass and aluminum don’t work together.
What can I do to stop this? Will a copper crush washer work? Or should it be aluminum? Or ?
You got them off after how many years, put it back exactly as you found it and no need to ever remove again. Copper probably. No reason to reinvent the wheel.
If these are 1-wire senders don’t forget that they get their electrical ground through the threads and washer. So don’t go too crazy with sealant or tape or whatever.