thank you guys.
The next step was the improvement of the hydraulic cylinders. The old version works well, but is a little bit leaky.
I've used O-Rings as seals and simple Stainless Rods. The upgrade is replacing the o- through x/quad-rings and using hard chrome plated rods.
It was not easy to find them in only 10mm diameter. But here they are
First item was the bucket cylinder.
A challenge for me was the new material C45/1.0503/AISI 1045 but it was easier than expected, including turning a m10 thread (a tap wrench doesn't work proper)
Additionally I've made better fitting pistons
To change the cylinder head from o ring to x ring grooves i need a 3mm wide internal grooving tool.
I've grind a rough thing from a blank
close but works
Aaaand after a 20 min testdig with really heavy clayey ground (directly from the excavators trailer to avoid too much dirt in the shop)
the cylinderhead is still sealed
Next step: upgrade the other cylinders.