There was no error message. I have deleted the services from the ArcGIS Server Manager. But in the folder arcgiscache the cache remained.
I have already tried to delete the cache in the way you mention, but I always got the error message that the service was busy.
I managed now after closing the Web Browser (maybe that was the problem as I had displayed the service before) and even restarting ArcGIS server.
Thanks for your help
Hilde