Rasmus steering
I've been struggling with my Rasmus steering for years. It's a fine set up, but after 35 years, neither HR nor Vetus supports the hydraulics any more.
I too had a leaking wheel pump - at the end of travel, the wheel would still turn slowly, in small pulses.
VETUS USA ( in Baltimore ) was able to help with this - they did some sort of rebuild, said it was not perfect, no more parts were available - but the pump has been fine the last 7 years.
The problem with changing the pump is you'll usually have to modify the helm housing to fit the new one (no direct replacement appears available ). The origonal vetus system should be 4 turns stop to stop.
You can easily bleed the system at the cylinder on the quadrant (under port side rear berth ). There's a bleed valve for each direction. You either need 2 people (one to turn the wheel, and one to bleed the air), or a tube and bottle of hydraulic fluid. If you fit a small bit of tubing to the bleed nipple, and then run that below the level of the fluid in a jar, one person can bleed the system without introducing air.
The process is just like bleeding the brakes on a car. You push fluid out the cylinder, until no more air is in the system. But the reservoir on the Vetus pump is tiny, so you need to keep topping the cylinder (or you'll introduce air at that end). I added a small plastic reservoir to my helm pump, so have a bit more fluid in the system to bleed.
My problem now is on the cylinder end. I have leaking seals, and Vetus is unable to supply repair parts. I've shopped around, gone to hydraulic shops, etc without finding new ones. So I'll probably be out $ 700, and have to modify the mounts to fit a new cylinder - all for want of $ 2.00 worth of seals !
Good luck with it.