Unloader Assembly 9.175-005.0

I replaced the unloaded however this did not fix the problem. I then removed the pump and tore it down. I inspected all the o rings and check valves. I saw nothing wrong with any parts. I cleaned all the parts and replaced 3 of the o rings. I did notice where the brass side of the pump fits against the aluminum side it was covered with so ... Read more mething that looked like smeared tar that was very hard to clean. It looked like melted o ring. The o rings were fine though! No signs of wear or damages. I choose to clean this and replace those o rings. Nothing I had would clean off this black tary substance. Carb clearer, break cleaner nothing I had. So out of desperation I used 0000 steel wool and break cleaner and lightly scribed the areas. After cleaning for several careful minutes I cleaned this part in an ultra sonic cleaner for about an hour. I wanted to make sure any of the steel wool that might have stayed was cleaned away so I also used air to blow off the part. Satisfied I\'d cleaned it as good as possible I put o rings in, changed the oil and assembled the pump installed it back on the engine and tested. It worked perfectly. I found several posts concerning Karchers design of this particular pump. Several complaints made about this very issue of how the pump housing joins. Seems the surging is a common issue even on pumps that have very little to no use at all. I\'ve used my repaired pump 3 or 4 times now about 45 minutes each go and so far my repair has held up. I may still just replace the pump but seeing so many complaints I may choose another pump manufacturer. I my case the unloaded wasn\'t needed as the old one was fine. Even the o rings I replaced wasn\'t needed because now the originals are installed and its continued to work. I think cleaning that tary substance off was the biggest problem because removing that allowed the pump sections to mate properly and be torqued together correctly. Keep in mind this pump had very few minutes of use before this problem showed up!

Remove old unloaded assembly & installed new one

replaced piston & spring lubed cnande oil replaced unloader and gasket