When you notice that spongy pedal feel or spot green fluid dripping under your MF, it's telling you something important. Your 300 series tractor's brake master cylinder is calling it quits, and this isn't the time to put off repairs. This replacement cylinder is built specifically for late-model 300 series tractors that use LHM mineral oil—and getting the right one means the difference between safe stops and brake failure when you're hauling that loaded grain wagon down a hill. What You're Getting Special seals designed for LHM mineral oil—no seal failure from using the wrong fluid Two-port design for your tractor's dual brake circuit system Precision-machined bore that gives you smooth, consistent brake feel Heavy-duty casting that won't crack under the pressure of daily farm work Direct replacement that fits like the original—no modifications needed Built for Real Farm Work These 300 series tractors were built when farming meant serious work—pulling loaded grain wagons, handling round balers on steep ground, and working long days with heavy implements. Whether you're navigating narrow farm lanes with a manure spreader or making those repeated loader runs during feeding time, reliable brakes aren't optional. This master cylinder ensures your brakes respond instantly when you need them most. Why LHM Fluid Matters Here's something that trips up a lot of folks: late 300 series MFs use LHM mineral oil because their brake slave cylinders sit inside the rear axle housing. If a cylinder leaks, that fluid mixes with your transmission oil. Regular DOT brake fluid would destroy your transmission—that's an expensive lesson you don't want to learn. This master cylinder comes with seals specifically made for mineral oil, and many farmers save money by using clean 10W-30 transmission oil instead of pricey LHM fluid. Installation Notes Bench bleed this cylinder before you install it—it'll save you headaches when bleeding the system later. Make sure those brake lines go to the right ports, or you'll have uneven braking. Start your system bleed at the wheel farthest from the master cylinder and work your way in. Remember: only LHM mineral oil or clean transmission oil goes in this system—never use DOT brake fluid.