D 100 Pickup L6-225 3.7L (1984)
Brake Bleeding: Service and Repair
About Brake System Bleeding
WHEN BLEEDING BRAKES REMEMBER...
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Brake fluid will remove paint and damage electrical connections. Use a drip pan and fender covers to protect the vehicle's finish and electrical
system.
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Always flush and bleed the brake hydraulic sys. when servicing the brakes, because:
Brake fluid absorbs moisture from the air, after 3-4 years of service the water content of the brake fluid may be as high as 6-7%. This
significantly reduces the boiling point of the brake fluid which may result in a soft pedal or brake failure during prolonged or severe braking.
Corrosion deposits and other contaminants gradually build up inside of the brake hydraulic sys. Check the bottom of the master-cylinder
reservoir for a build up of fine black silt. If any is present the brake fluid should be flushed.
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Never reuse brake fluid that has been drained from the brake system.
DOT 3,4 or DOT 5
As a general rule DOT 5 brake fluid should not be used in vehicles recommending DOT 3 or 4 type fluid.
DOT 5 brake fluid is silicone based. DOT 3 (standard) and DOT 4 (heavy-duty) are glycol-based. DOT 5 can be distinguished from conventional
brake fluids by its purple color (which comes from a dye).
DOT 5 silicone brake fluid won't mix with glycol-based brake fluid (creating concern over sludging if all old fluid isn't removed when a system is
refilled with silicone).
Silicone does not absorb moisture. DOT 5 brake fluid does not become contaminated with moisture over time as conventional DOT 3 and 4 brake
fluids do. Silicone is also chemically inert, nontoxic and won't damage paint like conventional brake fluid. It also has a higher boiling point.
Because of this, it is often marketed as a premium "lifetime" brake fluid. It is often used to preserve brake systems in antique vehicles and those
that sit for long periods of time between use.
Silicone also has slightly different physical properties and compressibility, making it unsuitable for ABS systems calibrated to work with DOT 3 or
4 brake fluid.
