FED-STD-791 Lubricants, Liquid Fuels, And Related Products, Testing Method OfThis test method standard is composed of standard test methods for sampling, inspecting and testing lubricants, liquid fuels and related products. It is issued pursuant to the Federal Property and Administration Services Act of 1949, as amended and its application to the purchase of commodities referred to herein is mandatory on all Federal agencies.

Pages 1 - - 44 - 45 - 46 - 47 - 48 - 49 - 50 - 51 - 52 - 53 - 54 - 55 - 56 - 57 - 58 - 59 - 60 - 61 - 62|||

'�NOTE:This draft dated 15 April 2006' by DasH - Page 53 of 460

FED-STD-791D

6.1.1.1 Wheel cylinder assemblies. The wheel cylinder assemblies shall be completely

disassembled. All rubber parts, with the exception of the cylinder boots, shall be discarded. The

expanders in the assembly shall also be discarded. All metal parts shall be cleaned with 95%

ethyl alcohol to remove preservative oils, grease, and dirt, then dried in a stream of dry air, and

examined for cuts, scores, galling, or pitting. Any part having any of these flaws shall be

replaced. Light stains on the cylinder walls shall be removed by rubbing with crocus cloth and

95% ethyl alcohol. Any cylinder which cannot be freed of stains by this procedure shall be

discarded.

6.1.1.2 Master cylinder assemblies. The master cylinder assemblies shall be completely

disassembled. All rubber parts, including the piston washer if it forms an integral part of the

primary cup, shall be discarded. The metal parts shall be cleaned, air-dried, examined for flaws,

and light stains removed from the cylinder walls in the manner specified for the wheel cylinder

assemblies (see 6.1.1.1). Any deficient parts shall be replaced. The cylinder's relief and supply

parts shall be inspected for burrs and wire-edge. If present, they may be removed with a burring

tool or a jeweler's file.

6.1.1.3 Rubber parts. The rubber parts to be used in the test shall be cleaned with a

lint-free cloth and 95% ethyl alcohol to remove all dirt and grease, then dried in a stream of dry

air and examined for cuts, molding flaws, or blisters. Any deficient part shall be discarded.

6.1.1.4 Tubing. The tubing used as brake fluid lines shall be flushed with 95% ethyl

alcohol, and dried by blowing dry air through it, prior to connecting to the test apparatus.

6.2 Initial measurements and tolerance.

6.2.1 Cylinders. The internal diameter of the master cylinder and of each of the wheel

cylinders shall be measured with a micrometer, to the nearest 0.0025 cm (0.001 in). Four

readings, approximately 45� apart, shall be taken on each cylinder, and their average considered

as the diameter of the cylinder. If the largest and smallest diametrical readings differ from each

other by more than 0.0075 cm (0.003 in), the cylinder in question shall be discarded.

6.2.2 Pistons. The external diameter of the master cylinder piston and of each of the

wheel cylinder pistons shall be measured with a micrometer, to the nearest 0.0025 cm (0.001 in).

Two readings, at right angles to each other, shall be taken on each piston, and their average

considered as the diameter of the piston. If the two readings differ from each other by more than

0.0025 cm (0.001 in) the piston in question shall be discarded.

6.2.2.1 Clearance of piston in cylinder. Each piston shall be checked for clearance

within the cylinder for which it is intended. If the clearance is less than 0.0075 cm (0.003 in) or

more than 0.0125 cm (0.005 in), the cylinder or the piston shall be replaced by another similar

part.

6.2.3 Rubber cups.