Good deal on the coolant leak.
This isn’t any help, but a comment, or opinion. I gave up trying to get noise out of CB’s. I’ve run them from the cigar lighter, tap a fuse and directly to the battery. Tried filters, just not good radios for keeping noise out of.
I like the President Bill I put in my Xterra. Has Automatic Squelch Control, so I don’t hear anything until I get a strong signal.