What an awesome post! I recently had to replace the pump on my Subaru pressure washer, which was probably comparable in difficulty to your fix, but required ~$50 in parts, so I feel more akin to you now than I did before I read the OP. I greatly admire some of the ad hoc tools and tricks you used to git 'r dun, like the steel wool on a stick and vinegar and baking soda cleaner. It is a great feeling to fix something and put it back into use, and by venturing to explore what was wrong with your Karcher and fix it you have made the world better, not just for you, but for me and everyone else on the planet.
Thanks!
Thank you for the very nice comment. It is a great feeling to fix something, A feeling that more people should get to experience. The amount of electrical waste I have found thrown away that just needed a simple fix is nearly criminal. I have found a Dyson Vacuum dleaner with just a blown fuse, a computer that had a corrupted Windows install and many things like that. All now living out their day in my service.
Schools should teach the basics of fixing things and with my son, like my father before me, I try to get him to help so he can catch the bug. (His little fingers come in very handy)
I homeschooled and taught my sons math with tape measures.