I have salvaged quite a few items to extract "precious" minor runes. Sadly my bank has become quite cluttered with runes now. Is there a way to combine say 3 of the same rune to get the next level? Or can I put 4 into the mystic forge and get a new possibly higher teir rune?
Sounds like you need a Horadric Cube! While there isn't any direct upgrade path, if you place four runes into the mystic forge, you will indeed get a random higher level rune out of it.