When I raise the 3 point hitch with a grader blade attached, it raise just fine and holds. The bucket on the loader will raise about 4 feet and stops. If I get off of the tractor and push down on the blade the bucket will raise to full height. As soon as I quit pushing down on the blade the bucket lower back to 4 feet off the ground. If I push down on the bucket it will lower all the way to the ground and won't raise again unless I lower both the blade and the bucket. The loader uses the 3 point hydraulic system to operate the bucket. PTO works fine, oil level is full. Can anyone clue me in as to what is wrong.