My 1946 Cletrac BD has a Heil HT-35 dozer blade. When I raise or lower the blade, it doesn't seem to stay in one position. I am constantly having to manipulate the hydraulic control lever to try and keep the blade level and in one place. Any hydraulic blades I've run before usually stay in one position unless you raise or lower it. Is this the way its supposed to be or is there something wrong with the controls? Sorry for the ignorance but I am no Operating Engineer.
Sounds like the controls or cylinders need new seals.
It's very common on old hydraulics. Could be the cylinders leaking internally, or the valves seeping.