Flushed with success after fixing my cheapo drill I turned
my attention to my jet washer.
This time it’s a quality German product - a
Kärcher 475. I think that a jet washer is essential if you're going to ride a bike
through the Scottish winter. It's great for blasting off dirt and road salt. I
bought mine a long time ago but recently its lost its mojo. It was just about
ok for cleaning the bike but when I tried to clean the patio I realised that
its pressure was well down. The gauge showed 40 bar instead of the usual 90 bar.
|  | 
| The gauge told me something was wrong | 
A pressure washer is just an electrical motor at one end and
a pump at the other. The motor seemed to be running ok so I though I'd take a
look at the pump. Now I don't really know how this works but, hey, that never
stopped me before. 
|  | 
| I didn't need to open up the electrics but when I did
there was a wiring diagram inside. Nice. | 
|  | 
| This sticker shows that the machine was made in 1990, so it
has given me a lot of years of service. It also tells me that cos φ, the power
factor, is 0.95….those Germans! | 
|  | 
| These pistons go in and out…. | 
|  | 
| …into these pump units. | 
|  | 
| 
 
The pump outputs. There's something funny going on…..a
broken O ring is jamming one valve open. 
 | 
|  | 
| O ring | 
It wasn't obvious where the O ring came from. There didn't seem
any way to further disassemble things so I cleaned it up and put it back together. And it worked fine. Back to 90 bar. 
|  | 
| Back to its patio cleaning best! | 
 So where did the O ring come from? Because the washer is now working fine I didn't think it came from inside. Looking about I found a self closing connection of a type I used in the past and that has an O ring that looks similar. The washer is suppose to have a mesh filter on the inlet but I removed this for some reason years ago. So mea culpa (as usual)
Now where did I put that filter?......