G 3500 1 Ton Van V6-262 4.3L (1985)
Brake Master Cylinder: Fundamentals and Basics
Parts Reminder List
RECOMMENDED PARTS
Basic Service, Replacement
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New or rebuilt master-cylinder
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Fresh/New brake fluid
If Overhaul is Required
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Master cylinder overhaul kit
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Brake assembly lubricant
Optional
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Aerosol brake cleaner.
New or Rebuilt Master Cylinder
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Always closely compare the new master-cylinder with the old master-cylinder. Minor variations in the size and depth of the primary piston
can result in significant reductions in braking performance.
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Examine the end of the master-cylinder where the pushrod contacts the piston. The depth and diameters of the pistons should match.
Brake Fluid
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Proper bench bleeding the master-cylinder and flushing the brake system will require a minimum of 16 oz of brake fluid.
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Never Mix DOT 3 (light amber in color) with DOT 5 (purple in color). There have been reports of damage to brake system seals when
DOT 3 and DOT 5 fluids are mixed
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Always store brake fluid in a sealed container. When left open brake fluid will absorb moisture from the air. This reduces the boiling point
of the brake fluid and could lead to a soft pedal or brake system failure during prolonged or emergency braking.
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Never add automatic transmission fluid, engine oil, or power steering fluid to the master-cylinder. Petroleum based fluids will cause the
rubber seals and gaskets in the brake system to swell and leak.
Master Cylinder Overhaul Kit
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Overhaul kits will often come with a variety cup and seal sizes. Closely match the old cups and seals with the new ones.
Brake Assembly Lubricant
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Assembly lubricant can greatly simply the master-cylinder overhaul process and prolong the life of the new seals.
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Clean brake fluid can be used to lubricate the master-cylinder bore during assembly but assembly lube is much slicker and prevents any
sticking or binding and possible damage to the new cups and seals.
Aerosol Brake Cleaner
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Commercially produced aerosol brake cleaners are designed to effectively clean brake systems while not leaving an oily residue.
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Do not use carburetor cleaner or solvent based products to clean brake system components. These products will leave a residue which
could contaminate the brake fluid or cause a reduction in braking performance.