SLOW BRAKE LEAK FROM CALIPER
I had the same happen a couple of years ago. Cleveland parts needed are a big O-ring for the brake piston, two per side, may also possibly need smaller ones for stub guide shaft on other side of piston. Total of 4 each per plane. Parts diagrams easily found online (Parker-Hannafin-Cleveland, www.parker.com).
Most important is to get the specific model # off of the caliper assembly so as to get the correct O-rings. There are too many models to count.There is an ID plate on the caliper, different from the wheel one. Disassemble the calipers, no need to remove from the plane. Have a helper slowly apply one side's brake and let the two pistons come out equally, so as to have enough piston to grab. As soon as one of the O-rings clears, all fluid is lost into your big pan. New O-rings, clean parts and calipers, a coat of 5606 everywhere, pistons back in. Repeat on 2nd side, makes no sense not to do both. Bleed system with fresh 5606, pressure check, check fluid level regularly, Calipers should be good for a decade.Remember to do a brake check on final.
Robert Forest N295P