I am in the market for a new pressure washer and have been doing some research, particularly on the Karchers...
This may be of some interest to you....
The K7 is the only machine with a brass cylinder head. It is rated at 160bar and has a duty cycle of 1 hour. This means it can be used for a maximum of 1 constant use and then must be shut off for at least 30 minutes - this is a water cooled machine.
The K5.2 and K5.7 have metal (not brass, not plastic) cylinder heads which are more durable than the plastic ones, but less durable than the K7. These are 130 bar machines. These machines have a duty cycle of 40 minutes before needing to be shut down for 30 mins. They are also water cooled.
The K4, 3 and 2 series all have plastic cylinder heads, and a duty cycle of 30 minutes, before needing 30 minutes cooling off period - these are air cooled machine.
The K1 series is the same as above but with only a 10 minute duty cycle....
According to Karcher, some of the common causes of the failed cylinder heads are:
1. Exceeding the duty cycle - i.e. working the machine too long before allowing cooling off periods
2. Insufficient supply of water to the machine from your tap
3. Not bleeding the system of all air before turning it on
4. Pushing dirty water through the machine
5. Using 'unauthorized' chemicals in the machine
6. The constant on/off nature of these machines causes cracks in the cylinder head itself,or the seals therein to fail.
From the above it would seem like the lower end models with the plastic cylinder heads are more prone to early failure - there are a lot of youtube videos showing detailing DIY repairs for these instances...
:xyxthumbs: