Hydro lifters made by a reputable German OE manufacturer.
Worn hydro lifters can be identified by a loud rattling noise right after engine start. The frequency changes with rpm.
Once oil pressure has been built up the noise may disappear. But it'll get worse and some day it won't disappear anymore.
If this happens it is highly recommended to replace all hydro lifters of the engine.
Hydro lifters cause excessive valve play. This again causes serious loss of engine power because the corresponding valve will not fully open anymore.
