Well there are a couple things you want to check first you need to find out if it is both the left side jacks or just one of them, if it is just one make sure all your fittings are tight, if you have a loosefitting or a bad o ring it can allow air to get into the system. if it is both on one side chances are it has air in the system and the way to blead it out is to drive up on some blocks on that side so that you can fully extend the jacks without all the weight of the coach on them and then let them sit for about a half hour and that will blead the air from the them. and if none of that works, it can only be one of two things you either have cylenders with a bad seals and the fluid is pushing back past the seals or you have a popit valve in the pump that is not closing all the way, and that can be caused by dirt particles or shavings in the fluid. if it is a valve it can be taken out and cleaned somewhat it is located on the side of the pump, it looks just like a big hex head bolt. you can try to clean it by pulling it out and making sure there is nothing in it. but make sure the cylinder does not have weight on it when you take it off
becuase you would have a real mess if it had weight on it. well if all that fails or you need some help or have any questions please call me on my cell phone anytime this weekend 269-816-1774
I hope this helps
Thanks Jason