You can rebuild a wheel cylinder but, my advice would be to just replace it with a new factory rebuilt one. You need to also replace the brake shoes at the same time. They are more likely soaked with brake fluid and are ruined. Replace both sides at the same time. Also, while you are doing this repair, I recommend you replace all the brake fluid in the system with fresh fluid from an unopened container, and bleed the brakes in this sequence. Start at the Right Rear, then LR, RF, and finish at the LF. The cause of the leaking wheel cylinder is probably water in the system that cause the cylinder to rust and leak.
Brake wheel cylinder or axle sealBrake wheel cylinder or axle seal
Where's the leak? Wheel cylinder, repair or replace, rusted line, replace, master cylinder, repair or replace.
Master cylinder empty (no brake fluid) Leak in brake line or wheel cylinder Defective master cylinder
Failed caliper, wheel cylinder, hose, or line.
There are 2 rubber seals on each end of the wheel cylinders and there leaking. REPLACE THE WHEEL CYLINDERS.
That sounds like a wheel cylinder leaking brake fluid.
Obviously you have a leak. Can be leaking at a caliber or wheel cylinder, which you can see on the backside of the wheel/tire. Can be leaking at a fitting, or at the master cylinder itself. You are just going to have to get under there and start looking.
It could be at the wheel brake cylinder or a junction at the rear axle.
The wheel cylinder has failed and will need replaced.
Check for vacuum leak or faulty EGR valve.
You could have a leaking wheel brake cylinder. It could also be a bad brake line or a bad master cylinder.
Replace brake lines or wheel cylinder which ever is leaking