It seems like every 2 years I have to replace the brake cylinders on this backhoe. I believe the problem is in the cap venting system. At night when it gets cool the pressure in the cylinder reservoir drops and air and humidity are drawn in. During the day it is expelled leaving moisture in the reservoir. These caps do not have the bellows in them. Has anyone found caps that fit that have these on them? Titan trailer cylinders seem close but I dont have one to try. I measure 18 tpi on these caps.