I have a L2900 which doesn’t have a dipstick to check the hydrauli fluid level….merely a sight-glass. I remember dumping fluid into it last summer, and I saw the fluid in the glass. I don't see the fluid level anymore, so I dumped the better part of a litre or so…still don’t see the level In the sight glass. Is it normal to lose that amount of hydro fluid over the course of a year? I’m scared if OVERFILLING it, just in case I’m wrong.