The Kärcher ... again

[akis]

This must be the 10th Kärcher that breaks. It just stops working. The motor is turning but there is no pressure. I have a wide range of electrical tools, drills, saws, vacuum cleaners etc that have lasted for decades of (ab)use. What is so special about those Karchers that they break with occasional only use?

[Berserk]

It's all about pump valves, what kind of model do you have?

I bet it's k5, and it has huge problem with pump head where drain valve sits

[BurningTantalum]

In my experience with these units, the small white plastic pump valves get stuck because of an accretion of minerals. I drop them in some fluid such as 'CLR' (can't recall what the active chemical is) or even vinegar, and clean them with a brush.
The other big 'killer' is freezing of the water left in the pump body, which will readily split the plastic or aluminium pump bodies. These splits are not easily visible unless the pump is under pressure.

When I lived in the UK, every unit that I picked up at the local dump had a split pump.
I run the pump of my unit for a few seconds with nothing connected to the inlet and outlet to purge the water before I store it after use.
Now I live in a frost-free area and no-one has heard of a pump splitting, but we have a slightly saline mains water supply which causes grief due to corrosion.
BT

[Lorenzo_1]

I had a couple of the cheap models with plastic head and valves. As others have found, the plastic valves kept seizing and then melting inside the head. Only option is to replace the head - easy/ish DIY but expensive compared with just buying a new machine at that time. You have to be careful with the long bolts than fit it to the alloy motor/drive cam body. They can strip quite easily. Karcher tech advised best way to avoid the problem is to buy higher-end model with brass head. Did that eventually and no further problems- but they're not cheap. If you use one regularly/long term then might be worth the capital cost.

[akis]

It is a model 300 I think, it is quite small, possibly the smallest. I do not know how I have come to own it. I have had a few models in the past and shared with my in-laws, so I do not know what is what.

I will buy the K4 model and hopefully it does not have plastic components.

[Rerouter]

We have had what appears to be an older K2 (model marking has rubbed off) for at least 4 years now. with no issues so far. the main thing is after use i tilt the thing on its side to drain the water out of the pump, and its stored in a dry location out of the sun,

So far running as well as the first time we had it, the spiral nozzle however is starting to clog up and takes a few fires to get running.

[SeanB]

I have had a lot of switch failures, as this model does use the mains switch dual purpose as power switch and pressure control. Thus the switch will eventually wear and the unit will not turn on if it has stopped for high pressure, other than by removing the lance end and draining it, then placing the end back, and the water hammer when opening it again is enough to allow the switch to operate again.

Aside from that, and the baby models not really being high pressure devices ( I miss the bigger WAP I had stolen, that one was quite capable of removing loose anything, and would get paint off any surface with ease, or remove anything at all, including being capable of cutting concrete if left on too long) the machines are good for occasional use, and at least Ryobi and Karcher actually do have spares for them. Drawback is they use an universal motor, not a decent induction motor, so life is going to be limited, and they will not run long periods without issue. 5 minutes on, 15 minutes off is the typical duty cycle I use, they do fail at higher duty cycles. Sadly a new unit is cheaper than a spare motor, though there at least you do get a spare lance and hose for when they fail as well, being that nasty thin high pressure pipe that cannot survive tight bends without kinking and failing.

[Berserk]

I will buy the K4 model and hopefully it does not have plastic components.

K4 have a plastic pump, k5 have composite plastic+metal pump, only k6-7 have full metal pump

[akis]

I will buy the K4 model and hopefully it does not have plastic components.

K4 have a plastic pump, k5 have composite plastic+metal pump, only k6-7 have full metal pump

The K4 that I just bought is not exactly cheap. I wonder is there another brand that do not use plastic components?

[Zucca]

Interesting. Are the 750 MX and 720 Mobile in the K7 family or not? Incredible how much know how there is here at the EEVBlog, even WAP.... I just love this.

[leftek]

I will buy the K4 model and hopefully it does not have plastic components.

K4 have a plastic pump, k5 have composite plastic+metal pump, only k6-7 have full metal pump

The K4 that I just bought is not exactly cheap. I wonder is there another brand that do not use plastic components?

The top Kranzle brand. You can see https://www.kraenzle.com/

[Berserk]

First digit stand for a x-hundred liters per hour, so yeah, that models relate to 7 series

k720 really good HP unit, just don't forget to check oil sometimes, k750 little bit cranky