P38A Dip stick

Hi all anyone know the size of the oring for the oil dipstick where it goes into the sump mines decided to give up the ghost and allow the contents of the sump to empty all over the road.
O it's a 1996 2.5td m51 engine

Check the cam cover internals and breather there should not be any positive pressure in the crank case. O'ring part number is LYX000140.

No pressure it doesn't seem to squirt out just weeping when engine is running, But a little goes along way with diesel engine oil. Looked worse on the road than it is, only lost about 250ml but that going up by the minute as it's still dripping into a bucket I've got under her. Are the oring just the rubber standard ones or a special material