Crockpot Beef Stroganoff

1 pound beef sirloin, cut into 1 inch cubes
1 can (family size) cream of mushroom soup
1/2 pound sliced button mushrooms
1 pkg dry onion soup mix
3 tablespoons sour cream
1 pound egg noodles

Mix soup, soup mix, and mushrooms together in bottom of crock pot. Stir in beef to coat. Cook on low in crock pot for 6-8 hours or high for 4-6 hours.Once meat is cooked thoroughly, turn off heat. Stir in sour cream.Cook noodles as directed on package. Serve beef mixture atop noodles.