There are several ways in which hydraulic jacks can become damaged, which is not immediately apparent during visual inspections (e.g., leaks around the valves or seals). Overall, they are safe if you follow the manufacturer guidelines on weight capacity and range. To remain safe, here are a few things you want to keep in mind: - Always place the jack under a support point on the vehicle capable of taking the load - Do not attempt to reposition a jack after you have already placed a load on it - Make sure that you are on a hard, flat surface before using the hydraulic jack or jack stands