I had similar but with a Sprinter, high pressure pump would leak when cold, as it warmed up it would seal up. a few thousand miles after it was sorted I had the bearings on the belt roller fail and the roller rolled off leaving the belt in a tangled mess and me with no power steering, water pump or alternator. Thinking was the diesel that had been flung around the belt had washed the bearing out.
Glad you got yours sorted
