Helpful hint to get Banjo fittings to seal better. Anneal the copper washers (seals). I have had issues with the copper washers being too hard and taking too much grunt to get them to seal. After annealing, you can feel the difference as you tighten the fitting. If they are not annealed properly, or have aged, they feel smooth. After annealing, they feel "rough", or like they "bite" as you tighten.
Makes a big difference.