B150 1/2 Ton Van V8-318 5.2L (1985)
Brake Master Cylinder: Fundamentals and Basics
Notes, Warnings, and Hints
REMOVAL
WARNING: DOT 3 or DOT 4 brake fluid is very corrosive to your vehicles finish.
Removing master cylinders can be a messy process. To prevent or minimize any possible damage perform the following:
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Siphon all brake fluid from the master-cylinder reservoir prior to removal.
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Use a fender cover to protect the vehicles finish.
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Use a drip pan to catch all fluid that leaks from the master-cylinder during removal.
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Any brake fluid which contacts the vehicles finish should be washed off immediately.
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Any brake fluid which drips onto electrical connections should be immediately removed (aerosol brake cleaner works well for this).
After the brake lines have been disconnected from the master-cylinder place vacuum caps over ends of the lines to prevent further leakage or
contamination.
Once the master-cylinder has been removed place it in a drip pan. Although the reservoir is empty, brake fluid trapped within the cylinder bore
will continue to slowly leak out.
INSTALLATION
Prior to installation the master-cylinder should be bench bled (this can be done on the vehicle but it is much easier on a workbench.
NOTE: Normal brake bleeding procedures will not remove air which is trapped in the cylinder bore area of a master-cylinder.
Attach the brake line fittings prior to snugging down the master-cylinder retaining bolts. The fittings are much easier to start turning when the
master-cylinder is still loose.
WARNING: Remember to tighten the retaining bolts after the brake lines are installed and tightened.
When snugging down the retaining bolts, alternately tighten them in small increments. This prevents the master-cylinder or push rod from
becoming cocked.
Upon installing the master-cylinder the entire brake system (front and rear) will need to be bled. Air enters the brake system as soon as the brake
lines are removed. It only requires a very small amount of air in the system to create a soft brake pedal.
WARNING: Never test drive a vehicle after a master-cylinder replacement until a firm brake pedal with a 75% reserve is established.