I have found lots of useful info here and This is my first post. Maybe this has been covered already. The wheel cylinders on my Dad’s XK had seized from sitting. Took them apart and found that they had been sleeved, put a kit in and all was well until after a test drive and found bad leaks. I wanted a way to test before re-installing. I put them in a vice loosely and tested with air. Some soapy water around the boots find leaks. I was going to toss them and decided to give it a last try and hone them. They seem to be leak free now. I hit them with about 100psi of air. You want to put them in a vice or it will shoot the piston out quite violently.
After I did mine with the stone honing, I wrapped a strip of Scotchbrite around the hone and Scotchbrited them for awhile, got them to a shiny mirror finish inside.
I recently rebuilt two brake cylinders that were previously sleeved in stainless. On one the piston had corroded and stuck in the bore. On the other the seal had started leaking. So sleeving does not free you from the need to rebuild from time to time (unless you go to DOT 5).
I noted that in the 30 years since they had been sleeved there was a tiny bit of wear in the bores. A fine grit brake hone cleaned them up quickly and they have been working fine 900 miles later.
I found that the other wheel cylinder was leaking between the sleeve and the aluminum body. I removed the dust boot and hit it with some air and soapy water and it was a stream of bubbles between the sleeve and the body. Probably years of heat cycles and the sleeve must have lost its bond. You all know what a joy it is to dis-mantle, clean, overhaul, bleed out, only to find more leaks. The air trick saved me alot of labor and head-aches. Got a new one and all is well now. Leak free finally!!! The hose in the pic is a spare 120 hose we had on hand. same thread as the banjo bolt.