I recently went to a Volvo Dealer to pick up some consumable copper washers for the bleed screw and pick up a few extra screws themselves. They have already changed the gun drilled screw to a cut slot down one side, the others fail (bust off) either by removing or tightening, My NEW D2-40 with 8 degree down angle trans has since new needed to be bled if let sit idle for more than a week. I asked him what his Idea may be, his response was, all the D models with the manual prime pumps have and do fail. The crimped fit top with the plunger attached to the bottom half of the pump leaks. There is no seal, only metal to metal crimp fit. He tested with a Volvo Rep 10, all 10 failed. The fix is to use (your choice) a sealant around the crimp fit to stop the leak. I used the black goo Multi-Calk and sealed it a couple of times let it dry, bleed the pump and have had success with no air leaks to date, and that's been about four months ago. So there you have it if you have the same symptoms, even if you don't, I'd seal it just because I don't want to be that guy getting towed in or worse, knock on wood......