Hello everyone,
I'm trying to wrap my mind around the HiLo trailer Hydraulic Lifting/Lowering design;
I sometimes wonder if the engineers did enough R&D testing on the hydraulic system back then to test and see if the system would hold up the weight of the top halve (which I suspect is at least 1500 lbs and upward on most HiLos) for a substantial amount of time, say...a week or two, and then check it for any slow downward creep and settling onto the safety bar. I think they figured when testing that if it stayed pressurized for a few days and not settling on the safety bar that it's an acceptable performance.

I have used and owned a lot of good quality hydraulic floor jacks that after a number of days holding up a HEAVY load they would leak down a little and lose some height. Most systems do.
If HiLo designed and intended the pressure in the Ram and the hydraulic system to stay up pressurized in a fully extended position for an extended period of time, and NOT creep downward onto the safety bar; then WHY for so many years have HiLo owners had problems with the top halve slowly settling on the safety bar?? Apparently the newer Hilos also leak down onto the safety bar after a few years of using their HiLo. I realize that hoses, seals and fittings get old and
will eventually start to fail, I think an additional mechanical locking system would have been nice, that way most or ALL of the top halve weight would be resting on it, relieving all the pressure off the hydraulics. Just my thoughts.

The truth is, hydraulic valves and check valves DO leak. They are not perfect. And have you seen the line feeding the cylinder? On mine it's plastic. The bar is part of the design. That's what it is there for. For that reason I always lower mine on the bar whenever I raise the top.

DunhamsDen, when I first got my HiLo I too would lower mine onto the safety bar after fully extending it. Now I extended fully and let it settle onto the safety bar on it's own; which happens in a couple of days. I haven't found any leaks visually, and if it's supposed to stay up and off of the safety bar...then I have a small undetectable leak somewhere. I can live with it.

These systems have been proven over many years of service.

If you see no signs of leaks, most likely the check valve is slowly leaking back into the resevoir. Don't worry about it as long as you do not have to add fluid.