I ask this question for a friend who has a 2009 Farmall 75C with cab and 4WD and about 3000 Hrs. He has to keep refilling the hydraulic brake reservoir. He doesn’t see any obvious leaks. He has a service manual and before doing any repair work he wonders if this is a common problem on the Farmall 75C and similar NH T4.75.
First of all, are you using the right brake fluid? It should be LHM liquid, which is mineral oil based. DOT 3 and 4 brake fluids are glycol based … not compatible with each other.
Several European-built CNH tractors that were based on existing New Holland products use this system, including the smaller Maxxum and Pumas. They also have a grease nipple for the outer shaft bearing because the brake prevents hydraulic oil from lubricating the bearing. Many operators neglect greasing this bearing.
Most similar tractors have a sensor in the master cylinder to illuminate a warning light on the dash to warn the operator when the brake fluid level is low. A good percentage of small Pumas / Maxxums and New Holland T6 and T7 tractors that come to the shop have this warning light on.