I have a 4310 with a 430 loader. The other day I lifted my lawnmower with my loader to help get under it to change my blades. As long the tractor was running it would hold it. But when I turned the tractor off the loader slowly leaked down. It took maybe 10 minutes and the lawn mower was back on the ground. If I park it at night and leave the laoder up by morning it will be back on the ground. Any suggestions?? Do I have a hydraulic leak?? I haven't seen any leaks.