are you using OEM starters or are you using a comparable starter from a local parts house? the reason I ask is I was having this problem I crossed the Hyster starter part number with my local supply house came up with a number got it for 2/3rds the price of an OEM but every one of them leaked within a week of installing them 4 starters latter I got an OEM one and have not had one leak since. Just a thought