When that space has been full of crud for years it turns into mush from the rain and snow. Once it becomes mush it turns into a paste and then it hardens. Best solution is to cut out a large circle (8 to10) inches in diameter on each side so u can get ur hand in there and scrape all the hardened crap out of there. A vacuum won't get all the hardened crud out of there. Once it's good and clean all u need to do is get a brush and some good undercoat and cover every inch inside there. Even with the big hole I still had to attach the brush to a long stick to get into all the nooks and crannies. Then u weld up the piece that u cut out, grind the welds and paint.
