Description
When your Massey Ferguson’s brakes start feeling spongy or you spot that telltale green LHM fluid dripping from the master cylinder, it’s time to rebuild rather than replace. A repair kit is available separately (part 4630) for rebuilding existing cylinders if the casting is still good. This comprehensive repair kit gives you everything you need to restore reliable braking to your 300 series tractor – often at half the cost of a new cylinder.
What You’re Getting
- Complete seal set specifically engineered for LHM mineral oil compatibility
- High-grade rubber compounds that resist the unique properties of mineral oil systems
- All necessary gaskets and O-rings for a complete cylinder rebuild
- Precision-molded seals that restore proper hydraulic pressure and stop leaks
- Quality components designed to handle the pressure and heat of heavy farm braking
Built for Real Farm Work
This brake master cylinder fits late Massey Ferguson 300 series tractors including models 340, 342, 350, 352, 355, 360, 362, 365, 375, 390, 390T, 398, and 399. These are the models with serial numbers after V39466 (approximately 1987 and later) that use the internal slave cylinder design. Your Massey Ferguson 300 series tractor handles serious work – from pulling loaded grain wagons to operating on steep hillsides with a round baler in tow. These tractors were built when farming meant heavy loads and long days, and reliable brakes aren’t optional.
Made to Last
Unlike most tractors that use DOT brake fluid, late 300 series MFs use LHM mineral oil because their brake slave cylinders are inside the rear axle housing. If a cylinder leaks, the fluid mixes with transmission oil – DOT fluid would destroy your transmission. This master cylinder is built with seals specifically designed for mineral oil. These aren’t generic seals – they’re formulated to withstand mineral oil’s unique properties and the demanding conditions of agricultural hydraulics.
Installation Notes
Before you start, make sure your cylinder casting isn’t cracked or severely scored – this kit only works with sound castings. Clean everything thoroughly during disassembly and inspect all mating surfaces. Many farmers successfully use 10W-30 transmission oil as an alternative to expensive LHM fluid. Always bench-bleed the rebuilt cylinder before installation and test your brakes thoroughly before getting back to work.
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