Karcher K4 Pressure Washer Leak (frost damage?)

9 Nov 2013
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United Kingdom

Our K4 pressure washer has developed a fault since last use. The motor runs continuously when switched on, and it leaks from somewhere in and around the pump. The only apparent fault is a a crack in the pump housing where the detergent feed connects just above the figure "8" in the drawing. When the water supply is connected there is a very slow leak from that point, maybe a drop or so per second. However it doesn't appear to be the main issue. When the pump runs water seems to spray out all the way round. I'm finding it hard or impossible to see where it's actually coming from because the spray covers everything.

Any suggestions on narrowing it down, or of known problem locations that might not look obvious? I can't see any other damage apart from that hairline crack. I was thinking maybe wrap masking tape around various places and see where the tape gets blown off.

Moving on, assuming I can get it fixed I have a suspicious that this might have been caused by the thing freezing, however there doesn't seem to be any way of draining it. Instructions just say to drain by releasing the pressure, but that must still leave the insides full of water. Again, any ideas on how to drain down properly?

Thanks in advance, Tony S

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Yep, part 8 is the one that fails....5 is a steel clamp that holds it all together. Its a common failure I'm afraid, causing pressurised water to circulate around the pump head - hence the Brr Brr Brr sound when its running.
As for draining it, I disconnect the water feed then the lance hose, running the machine until no more water comes out. Probably not foolproof though!
John :)
Cheers. One option is just to replace part 8 and the triangular O ring and see how it works. I'm just puzzled because the only visible damage on that part is just the crack in the detergent connection (which I don't think is even on the high pressure side), but water sprays out in all directions when the pump runs. Are these devices prone to leaks from between components, for example between that part 8 and the cylinder head part 11, or between cylinder (11) and the metal motor assembly?
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Part 8 is the high pressure chamber and prone to internal cracks - the machines aren't prone to leaking between the chambers as the O rings are of good quality.
The detergent application normally works on reduced back pressure in the lance so you don't see leaks there.
John :)
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Another quick question if you don't mind, what would be the right sort of grease to use when assembling? To hand I have general purpose silicone grease (nice and slippery), stuff called Turbogel that's a synthetic grease with teflon (as recommend for marine toilets). I don't have anything white.
I use a red rubber grease by Granville......it won't rot the O ring seals and tends to stay where it's put.
Silicone grease is just fine too.
John :)
Thanks for the pointers, I'd hoped to be posting a success story but no such luck. First part I bought, although from a Karcher service centre and explicitly listed for my exact model (1.180-151.0) did not fit, the detergent connector was the wrong size, too large. The dealer said that's the only part listed so all he could do was refund. Second Karcher agent said there's two parts, the earlier ones the detergent connector is 26mm outside diameter, later ones 22mm. He confirmed that my machine needs the 22mm. But that doesn't fit either. Everything fits and connects OK, except when fitting the last part the high pressure outlet (part 1 on the drawing). This doesn't fit fully onto the spigot on the control head, meaning the retained can't be fitted (and it probably wouldn't line up with the housing either). I don't know where to go from here.

Old part ..


New one ..

Everything looks sort of ok, at least where the fit matters......is it possible to slide the retainer clip (part 2) into the slots? It doesn't look as if the head can be pushed any further in.
If no go, maybe take the unit to the Karcher agent for them to explain......nowt's easy, is it :( Just wondering if the new part has been upgraded from the original.
Maybe you could split the parts again and give us another photo of the old and new side by side, and not located in the pump body?
John :)
The fitting does not fit far enough for the retainer. Old and new side by side. There's no apparent external height difference.

The shape is different though, for example on the new part (left hand above) the slot for the retainer is wider. Old, then new shown below ..



Next step will be to contact Karcher on Monday. They gave me the brush off initially saying they'd only discuss parts with dealers. However if the dealers can't help, or Karcher's been supplying them with dud parts or info then it's back to Karcher. Stage two is scrap the thing and buy a different make. I'm getting some domestic pressure to do that as it's taking so much time faffing around with this, and getting two sets of dud parts as well starts to suggest they're unmaintainable.
Sorry I can't add anything more Tony but many thanks for the excellent pics!
I'd be interested to hear what Karcher come up with if you wouldn't mind posting back.
John :)
Hopefully now fixed. The service agent asked me to send the original control head, the new replacement, and the outlet elbow. He first tried a new elbow on the suspect head, and it didn't fit either. He then tried another control head, same part number, and it fitted right away. I'm just waiting for the parts back.

Prior to that I'd tracked down the exact reason for the issue, a part on the elbow that needs a 10mm hole to fit into, and the new control head only had 9.5mm. See photos ..
Elbow ..
Original control head ..
And new ..

Karcher were almost completely useless. They didn't bitch as much as I feared about the idea of an end user working on the machine, but there was an element of that. The first lady sent out a parts list which clearly showed three internal variations but also confirmed that the part I'd received was correct. The part sent earlier by the other service centre didn't appear at all. Second lady also sent out a parts list, but hers was dated Jan 2013, showed only one variant and only had the original and incorrect part listed.
I had an internal Leak as well, but mine was on both plastic pieces (nr 8 and nr 11).
You could not see any damage or cracks in the plastic visually.

See video when it is in operating (nr 11 is leaking), in the meantime i had already fixed nr 8.


Replaced it and it was up and running again.
Karcher were almost completely useless.
When my K7 packed up under warranty, they sent me a new lance (it was Bluetooth operated). Trouble was, they sent one for a K4 and that was despite me telling them and sending them pictures of the model and serial number. I phoned them up and they then sent me a lance for a …….K4 again! I phoned them back up and they sent me the correct lance. It didn’t cure the problem so they collected the whole machine including the original Lance, repaired it and sent it back to me. They also told me to keep the brand new lance as a spare for my trouble!

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