Join Date: Jan 2010
My Motorhome: Hymer B584
Get a round bit of wood like 3" or 4" of brush handle that will fit in the filler hole. Wrap insulation / masking / cellotape round it until it is slightly too big to fit in the hole and then screw it in.
That should make it drivable, with some oil, and be a reasonable temporary fix till you get the culprits to sort it out