you are much welcomed:
1-you should get visa Bahrain crossing saudia. it coast 270 qr.
papers required (id copy , Car license copy passport , one pic)
many offices doing it.
2-trip take around 5-6 hours including the border process (one way).
3- better to move in day light as the no lights in the road.
4-better to not go alone.
5-make sure to full petrol before start.
6-make sure from tires and all are ok .
7-use google map for the way

for any data dont hesitate to contact

all my data is free