M604 steering leak

I've been rebuilding the steering on a 604, new O-rings, gaskets etc. It's gone back together very nicely except for one problem. After I put oil in it (up to the bottom of the plug on the right-hand side of the housing) it started to slowly leak at the right hand end plug. It's coming from around the piston sleeve where a new gasket was fitted.

I pulled it apart and found a couple of tiny dents/bends in the edge of the 45 sleeve flange. These would have stopped the gasket seating properly. Problem found, I thought. I tapped them straight and reinstalled with a small bead the silicon each side of the gasket thinking that would provide a good seal. Still leaking, unfortunately.

Not sure where to go next, but a couple of thoughts:

Use an O-ring instead of the gasket if I can find one with a small enough cross section at that diameter. Doubtful they are available.

Ditch the gasket and reinstall sleeve with a generous bead of silicon gasket maker behind the flange. It would be important to drain the oil first and make sure the area is thoroughly clean.

I'm leaning towards the latter as the first option but interested to find out what the experts think, or if somebody has solved this problem previously.

Jack

All sorted. I drained the oil, pulled the sleeve and cleaned it all thoroughly. Then applied a generous application of blue silicon, quite a bit more than previously, and the leak has gone.

I now have just an ever so slight leak from around the input shaft even after a new O-ring, but can live with it. It runs back under the side rail but even after a few days hadn't dripped onto the floor. The oil in it is quite light. Probably should have 90 or 140, I'm guessing? I'll change over to that - it might help.

Jack