Howdy all! I'll just cut right to the chase.... I've got a 44" Zturn (mdl# LHP4420KC) with a Kohler engine that is spitting hydro fluid from the vented cap on the reservoir. The operator says it starts leaking after about 10 minutes of use. the reservoir is not overfull, and I don't think there's any air in the system (not foamy) any ideas what else it could be?