571.116—Standard No. 116; Motor vehicle brake fluids.
S1. Scope. This standard specifies requirements for fluids for use in hydraulic brake systems of motor vehicles, containers for these fluids, and labeling of the containers.
S2. Purpose. The purpose of this standard is to reduce failures in the hydraulic braking systems of motor vehicles which may occur because of the manufacture or use of improper or contaminated fluid.
S3. Application. This standard applies to all fluid for use in hydraulic brake systems of motor vehicles. In addition, S5.3 applies to passenger cars, multipurpose passenger vehicles, trucks, buses, trailers, and motorcycles.
S4. Definitions.
Blister means a cavity or sac on the surface of a brake cup.
Brake fluid means a liquid designed for use in a motor vehicle hydraulic brake system in which it will contact elastomeric components made of styrene and butadiene rubber (SBR), ethylene and propylene rubber (EPR), polychloroprene (CR) brake hose inner tube stock or natural rubber (NR).
Chipping means a condition in which small pieces are missing from the outer surface of a brake cup.
Duplicate samples means two samples of brake fluid taken from a single packaged lot and tested simultaneously.
Hydraulic system mineral oil means a mineral-oil-based fluid designed for use in motor vehicle hydraulic brake systems in which the fluid is not in contact with components made of SBR, EPR or NR.
Packager means any person who fills containers with brake fluid that are subsequently distributed for retail sale.
Packaged lot is that quantity of brake fluid shipped by the manufacturer to the packager in a single container, or that quantity of brake fluid manufactured by a single plant run of 24 hours or less, through the same processing equipment and with no change in ingredients.
Scuffing means a visible erosion of a portion of the outer surface of a brake cup.
A silicone base brake fluid (SBBF) is a brake fluid which consists of not less than 70 percent by weight of a diorgano polysiloxane.
Sloughing means degradation of a brake cup as evidenced by the presence of carbon black loosely held on the brake cup surface, such that a visible black streak is produced when the cup, with a 500 ±10 gram deadweight on it, is drawn base down over a sheet of white bond paper placed on a firm flat surface.
Stickiness means a condition on the surface of a brake cup such that fibers will be pulled from a wad of U.S.P. absorbent cotton when it is drawn across the surface.
S5. Requirements. This section specifies performance requirements for DOT 3, DOT 4 and DOT 5 brake fluids; requirements for brake fluid certification; and requirements for container sealing, labeling and color coding for brake fluids and hydraulic system mineral oils. Where a range of tolerances is specified, the brake fluid shall meet the requirements at all points within the range.
S5.1Brake fluid. When tested in accordance with S6, brake fluids shall meet the following requirements:
S5.1.1Equilibrium reflux boiling point (ERBP ). When brake fluid is tested according to S6.1, the ERBP shall not be less than the following value for the grade indicated:
S5.1.2Wet ERBP. When brake fluid is tested according to S6.2, the wet ERBP shall not be less than the following value for the grade indicated:
S5.1.3. Kinematic viscosities. When brake fluid is tested according to S6.3, the kinematic viscosities in square millimeters per second at stated temperatures shall be neither less than 1.5 mm 2 /s at 100 °C. (212 °F.) nor more than the following maximum value for the grade indicated:
S5.1.4pH value. When brake fluid, except DOT 5 SBBF, is tested according to S6.4, the pH value shall not be less than 7.0 nor more than 11.5.
S5.1.5Brake fluid stability.
S5.1.5.1High-temperature stability. When brake fluid is tested according to S6.5.3 the ERBP shall not change by more than 3 °C. (5.4 °F.) plus 0.05° for each degree that the ERBP of the fluid exceeds 225 °C. (437 °F.).
S5.1.5.2Chemical stability. When brake fluid, except DOT 5 SBBF, is tested according to S6.5.4, the change in temperature of the refluxing fluid mixture shall not exceed 3.0 °C (5.4 °F.) plus 0.05° for each degree that the ERBP of the fluid exceeds 225 °C (437 °F.).
S5.1.6Corrosion. When brake fluid is tested according to S6.6—
| Test strip material | Maximum permissible weight change, mg./sq. cm. of surface |
|---|---|
| Steel, tinned iron, cast iron | 0.2 |
| Aluminum | .1 |
| Brass, copper | .4 |
(b)
Excluding the area of contact (13 ±1 mm. ( 1/2 ± 1/32 inch) measured from the bolt hole end of the test strip), the metal test strips shall not show pitting or etching to an extent discernible without magnification;
(c)
The water-wet brake fluid at the end of the test shall show no jelling at 23 ±5 °C (73.4 ±9 °F.);
(d)
No crystalline deposit shall form and adhere to either the glass jar walls or the surface of the metal strips;
(e)
At the end of the test, sedimentation of the water-wet brake fluid shall not exceed 0.10 percent by volume;
(f)
The pH value of water-wet brake fluid, except DOT 5 SBBF, at the end of the test shall not be less than 7.0 nor more than 11.5;
(g)
The cups at the end of the test shall show no disintegration, as evidenced by blisters or sloughing;
(h)
The hardness of the cup shall not decrease by more than 15 International Rubber Hardness Degrees (IRHD); and
S5.1.7Fluidity and appearance at low temperature. When brake fluid is tested according to S6.7, at the storage temperature and for the storage times given in Table II—
(b)
Upon inversion of the sample bottle, the time required for the air bubble to travel to the top of the fluid shall not exceed the bubble flow times shown in Table II; and
(c)
On warming to room temperature, the fluid shall resume the appearance and fluidity that it had before chilling.
| Storage temperature | Storage time (hours) | Maximum bubble flow time (seconds) |
|---|---|---|
| Minus 40 ±2 °C. (minus 40 ±3.6 °F.) | 144 ±4.0 | 10 |
| Minus 50 ±2 °C. (minus 58 ±3.6 °F.) | 6 ±0.2 | 35 |
S5.1.8 [Reserved]
S5.1.9Water tolerance. (a) At low temperature. When brake fluid is tested according to S6.9.3(a)—
(2)
Upon inversion of the centrifuge tube, the air bubble shall travel to the top of the fluid in not more than 10 seconds;
(3)
If cloudiness has developed, the wet fluid shall regain its original clarity and fluidity when warmed to room temperature; and
S5.1.10Compatibility.
(a) At low temperature.
When brake fluid is tested according to S6.10.3(a), the test specimen shall show no sludging, sedimentation, or crystallization. In addition, fluids, except DOT 5 SBBF, shall show no stratification.
S5.1.11Resistance to oxidation. When brake fluid is tested according to S6.11—
(a)
The metal test strips outside the areas in contact with the tinfoil shall not show pitting or etching to an extent discernible without magnification;
(b)
No more than a trace of gum shall be deposited on the test strips outside the areas in contact with the tinfoil;
S5.1.12Effects on cups. When brake cups are subjected to brake fluid in accordance with S6.12—
(a)
The increase in the diameter of the base of the cups shall be not less than 0.15 mm. (0.006 inch) or more than 1.40 mm. (0.055 inch);
(b)
The decrease in hardness of the cups shall be not more than 10 IRHD at 70 °C. (158 °F.) or more than 15 IRHD at 120 °C. (248 °F.), and there shall be no increase in hardness of the cups; and
S5.1.13Stroking properties. When brake fluid is tested according to S6.13—
(a)
Metal parts of the test system shall show no pitting or etching to an extent discernible without magnification;
(c)
The average decrease in hardness of seven of the eight cups tested (six wheel cylinder and one master cylinder primary) shall not exceed 15 IRHD. Not more than one of the seven cups shall have a decrease in hardness greater than 17 IRHD;
(d)
None of the eight cups shall be in an unsatisfactory operating condition as evidenced by stickiness, scuffing, blisters, cracking, chipping, or other change in shape from its original appearance;
(e)
None of the eight cups shall show an increase in base diameter greater than 0.90 mm (0.035 inch);
(i)
The total loss of fluid during the 100 strokes at the end of the test shall not exceed 36 milliliters;
(l)
Brake cylinders shall be free of deposits that are abrasive or that cannot be removed when rubbed moderately with a nonabrasive cloth wetted with ethanol.
S5.1.14 Fluid color. Brake fluid and hydraulic system mineral oil shall be of the color indicated:
DOT 3, DOT 4, and DOT 5.1 non-SBBF—colorless to amber.
DOT 5 SBBF—purple.
Hydraulic system mineral oil—green.
S5.2Packaging and labeling requirements for motor vehicle brake fluids.
S5.2.1Container sealing. Each brake fluid or hydraulic system mineral oil container with a capacity of 177 mL or more shall be provided with a resealable closure that has an inner seal impervious to the packaged brake fluid. The container closure shall include a tamper-proof feature that will either be destroyed or substantially altered when the container closure is initially opened.
S5.2.2Certification, marking, and labeling.
S5.2.2.1Each manufacturer of a DOT grade brake fluid shall furnish to each packager, distributor, or dealer to whom he delivers brake fluid, the following information:
(b)
The grade (DOT 3, DOT 4, DOT 5) of the brake fluid. If DOT 5 grade brake fluid , it shall be further distinguished as “DOT 5 SILICONE BASE” or “DOT 5.1 NON-SILICONE BASE.”
S5.2.2.2Each packager of brake fluid shall furnish the information specified in paragraphs (a) through (g) of this S5.2.2.2 by clearly marking it on each brake fluid container or on a label (labels) permanently affixed to the container, in any location except a removable part such as a lid. After being subjected to the operations and conditions specified in S6.14, the information required by this section shall be legible to an observer having corrected visual acuity of 20/40 (Snellen ratio) at a distance of 305 mm, and any label affixed to the container in compliance with this section shall not be removable without its being destroyed or defaced.
(e)
Designation of the contents as “DOT—MOTOR VEHICLE BRAKE FLUID” (Fill in DOT 3, DOT 4, DOT 5 SILICONE BASE, or DOT 5.1 NON-SILICONE BASE as applicable).
(2)
KEEP BRAKE FLUID CLEAN AND DRY. Contamination with dirt, water, petroleum products or other materials may result in brake failure or costly repairs.
(3)
STORE BRAKE FLUID ONLY IN ITS ORIGINAL CONTAINER. KEEP CONTAINER CLEAN AND TIGHTLY CLOSED TO PREVENT ABSORPTION OF MOISTURE.
(4) CAUTION:
DO NOT REFILL CONTAINER, AND DO NOT USE FOR OTHER LIQUIDS. (Not required for containers with a capacity in excess of 19 L.)
S5.2.2.3Each packager of hydraulic system mineral oil shall furnish the information specified in paragraphs (a) through (e) of this S5.2.2.3 by clearly marking it on each brake fluid container or on a label (labels) permanently affixed to the container, in any location except a removable part such as a lid. After being subjected to the operations and conditions specified in S6.14, the information required by this section shall be legible to an observer having corrected visual acuity of 20/40 (Snellen ratio) at a distance of 305 mm and any label affixed to the container in compliance with this section shall not be removable without its being destroyed or defaced.
(d)
Designation of the contents as “HYDRAULIC SYSTEM MINERAL OIL” in capital letters at least 3 mm high.
(2)
Hydraulic System Mineral Oil is NOT COMPATIBLE with the rubber components of brake systems designed for use with DOT brake fluids.
(3)
KEEP HYDRAULIC SYSTEM MINERAL OIL CLEAN. Contamination with dust or other materials may result in brake failure or costly repair.
(4) CAUTION:
STORE HYDRAULIC SYSTEM MINERAL OIL ONLY IN ITS ORIGINAL CONTAINER. KEEP CONTAINER CLEAN AND TIGHTLY CLOSED. DO NOT REFILL CONTAINER OR USE OTHER LIQUIDS. (The last sentence is not required for containers with a capacity in excess of 19 L.)
S5.2.2.4 If a container for brake fluid or hydraulic system mineral oil is not normally visible but designed to be protected by an outer container or carton during use, the outer container or carton rather than the inner container shall meet the labeling requirements of S5.2.2.2 or S5.2.2.3, as appropriate.
S5.3Motor vehicle requirement. Each passenger car, multipurpose passenger vehicle, truck, bus, trailer, and motorcycle that has a hydraulic brake system shall be equipped with fluid that has been manufactured and packaged in conformity with the requirements of this standard.
S6. Test procedures.
S6.1Equilibrium reflux boiling point. Determine the ERBP of a brake fluid by running duplicate samples according to the following procedure and averaging the results.
S6.1.1Summary of procedure. Sixty milliliters (ml.) of brake fluid are boiled under specified equilibrium conditions (reflux) at atmospheric pressure in a 100-ml. flask. The average temperature of the boiling fluid at the end of the reflux period, corrected for variations in barometric pressure if necessary, is the ERBP.
S6.1.2Apparatus. (See Figure 1) The test apparatus shall consist of—
(a) Flask.
(See Figure 2) A 100-ml. round-bottom, short-neck heat-resistant glass flask having a neck with a 19/38 standard taper, female ground-glass joint and a side-entering tube, with an outside diameter of 10 millimeters (mm.), which centers the thermometer bulb in the flask 6.5 mm. from the bottom;
(b) Condenser.
A water-cooled, reflux, glass-tube type, condenser having a jacket 200 mm. in length, the bottom end of which has a 19/38 standard-taper, drip-tip, male ground-glass joint;
(c) Boiling stones.
Three clean, unused silicon carbide grains (approximately 2 mm. (0.08 inch) in diameter, grit No. 8);
(d) Thermometer.
Standardized calibrated partial immersion (76 mm.), solid stem, thermometers conforming to the requirements for an ASTM 2C or 2F, and an ASTM 3C or 3F thermometer; and
(e) Heat source.
Variable autotransformer-controlled heating mantle designed to fit the flask, or an electric heater with rheostat heat control.
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Code of Federal Regulations
S6.1.3Preparation of apparatus. (a) Thoroughly clean and dry all glassware.
(b)
Insert thermometer through the side tube until the tip of the bulb is 6.5 mm. ( 1/4 inch) from the bottom center of the flask. Seal with a short piece of natural rubber, EPDM, SBR, or butyl tubing.
(d)
Attach the flask to the condenser. When using a heating mantle, place the mantle under the flask and support it with a ring-clamp and laboratory-type stand, holding the entire assembly in place by a clamp. When using a rheostat-controlled heater, center a standard porcelain or hard asbestos refractory, having a diameter opening 32 to 38 mm., over the heating element and mount the flask so that direct heat is applied only through the opening in the refractory. Place the assembly in an area free from drafts or other types of sudden temperature changes. Connect the cooling water inlet and outlet tubes to the condenser. Turn on the cooling water. The water supply temperature shall not exceed 28 °C. (82.4 °F.) and the temperature rise through the condenser shall not exceed 2 °C. (3.6 °F.).
S6.1.4Procedure. Apply heat to the flask so that within 10 ±2 minutes the fluid is refluxing in excess of 1 drop per second. The reflux rate shall not exceed 5 drops per second at any time. Immediately adjust the heating rate to obtain an equilibrium reflux rate of 1 to 2 drops per second over the next 5 ±2 minutes. Maintain this rate for an additional 2 minutes, taking four temperature readings at 30-second intervals. Record the average of these as the observed ERBP. If no reflux is evident when the fluid temperature reaches 260 °C (500 °F), discontinue heating and report ERBP as in excess of 260 °C (500 °F).
S6.1.5Calculation. (a) Thermometer inaccuracy. Correct the observed ERBP by applying any correction factor obtained in standardizing the thermometer.
(b) Variation from standard barometric pressure.
Apply the factor shown in Table III to calculate the barometric pressure correction to the ERBP.
| Observed ERBP corrected for thermometer inaccuracy | Correction per 1 mm difference in pressure a | |
|---|---|---|
| °C. | ( °F.) | |
| 100 °C. (212 °F.) to 190 °C. (374 °F.) | 0.039 | (0.07) |
| Over 190 °C. (374 °F.) | 0.04 | (0.08) |
| a To be added in case barometric pressure is below 760 mm.; to be subtracted in case barometric pressure is above 670 mm. | ||
(c)
If the two corrected observed ERBP's agree within 2 °C. (4 °C. for brake fluids having an ERBP over 230 °C./446 °F.) average the duplicate runs as the ERBP; otherwise, repeat the entire test, averaging the four corrected observed values to determine the original ERBP.
S6.2Wet ERBP. Determine the wet ERBP of a brake fluid by running duplicate samples according to the following procedure.
S6.2.1.Summary of procedure. A 350 ml. sample of the brake fluid is humidified under controlled conditions; 350 ml. of SAE triethylene glycol monomethyl ether, brake fluid grade, referee material (TEGME) as described in appendix E of SAE Standard J1703 Nov. 83, “Motor Vehicle Brake Fluid,” November 1983, is used to establish the end point for humidification. After humidification, the water content and ERBP of the brake fluid are determined.
S6.2.2Apparatus for humidification. (See Figure 3).
Test apparatus shall consist of—
(a) Glass jars.
Four SAE RM-49 corrosion test jars or equivalent screwtop, straight-sided, round glass jars each having a capacity of about 475 ml. and approximate inner dimensions of 100 mm. in height by 75 mm. in diameter, with matching lids having new, clean inserts providing water-vapor-proof seals;
(b) Desiccator and cover.
Two bowl-form glass desiccators, 250-mm. inside diameter, having matching tubulated covers fitted with No. 8 rubber stoppers; and
(c) Desiccator plate.
Two 230-mm. diameter, perforated porcelain desiccator plates, without feet, glazed on one side.
S6.2.3Reagents and materials. (a) Distilled water, see S7.1.
S6.2.4Preparation of apparatus. Lubricate the ground-glass joint of the desiccator. Pour 450 ±10 ml. of distilled water into each desiccator and insert perforated porcelain desiccator plates. Place the desiccators in an oven with temperature controlled at 50 ±1 °C. (122 ±1.8 °F.) throughout the humidification procedure.
S6.2.5Procedure. Pour 350 ±5 ml. of brake fluid into an open corrosion test jar. Prepare in the same manner a duplicate test fluid sample and two duplicate specimens of the SAE TEGME referee material (350 ±5 ml. of TEGME in each jar). The water content of the SAE TEGME fluid is adjusted to 0.50 ±0.05 percent by weight at the start of the test in accordance with S7.2. Place one sample each of the test brake fluid and the prepared TEGME sample into the same desiccator. Repeat for the second sample of test brake fluid and TEGME in a second desiccator. Place the desiccators in the 50 °C. (122 °F.) controlled oven and replace desiccator covers. At intervals, during oven humidification, remove the rubber stoppers in the tops of desiccators. Using a long needled hypodermic syringe, take a sample of not more than 2 ml. from each TEGME sample and determine its water content. Remove no more than 10 ml. of fluid from each SAE TEGME sample during the humidification procedure. When the water content of the SAE fluid reaches 3.70 ±0.05 percent by weight (average of the duplicates). remove the two test fluid specimens from their desiccators and promptly cap each jar tightly. Allow the sealed jars to cool for 60 to 90 minutes at 23° ±5 °C. (73.4° ±9 °F.). Measure the water contents of the test fluid specimens in accordance with S7.2 and determine their ERBP's in accordance with S6.1. If the two ERBPs agree within 4 °C. (8 °F.), average them to determine the wet ERBP; otherwise repeat and average the four individual ERBPs as the wet ERBP of the brake fluid.
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S6.3 Kinematic viscosities. Determine the kinematic viscosity of a brake fluid in mm 2 /s by the following procedure. Run duplicate samples at each of the specified temperatures, making two timed runs on each sample.
S6.3.1Summary of the procedure. The time is measured for a fixed volume of the brake fluid to flow through a calibrated glass capillary viscometer under an accurately reproducible head and at a closely controlled temperature. The kinematic viscosity is then calculated from the measured flow time and the calibration constant of the viscometer.
S6.3.2Apparatus.
(a) Viscometers.
Calibrated glass capillary-type viscometers, ASTM D2515-66, “Standard Specification for Kinematic Glass Viscometers,” measuring viscosity within the precision limits of S6.4.7. Use suspended level viscometers for viscosity measurements at low temperatures. Use Cannon-Fenske Routine or other modified Ostwald viscometers at ambient temperatures and above.
(b) Viscometer holders and frames.
Mount a viscometer in the constant-temperature bath so that the mounting tube is held within 1° of the vertical.
(c) Viscometer bath.
A transparent liquid bath of sufficient depth such that at no time during the measurement will any portion of the sample in the viscometer be less than 2 cm. below the surface or less than 2 cm. above the bottom. The bath shall be cylindrical in shape, with turbulent agitation sufficient to meet the temperature control requirements. For measurements within 15° to 100 °C. (60° to 212 °F.) the temperature of the bath medium shall not vary by more than 0.01 °C. (0.02 °F.) over the length of the viscometers, or between the positions of the viscometers, or at the locations of the thermometers. Outside this range, the variation shall not exceed 0.03 °C. (0.05 °F.).
(d) Thermometers.
Liquid-in-Glass Kinematic Viscosity Test Thermometers, covering the range of test temperatures indicated in Table IV and conforming to ASTM E1-68, “Specifications for ASTM Thermometers,” and in the IP requirements for IP Standard Thermometers. Standardize before use (see S6.3.3(b)). Use two standardized thermometers in the bath.
| Temperature range | For tests at | Subdivisions | Thermometer number | ||||
|---|---|---|---|---|---|---|---|
| °C. | °F. | °C. | °F. | °C. | °F. | ASTM | IP |
| Minus 55.3 to minus 52.5 | Minus 67.5 to minus 62.5 | Minus 55 | Minus 67 | 0.05 | 0.1 | 74 F | 69 F. or C. |
| Minus 41.4 to minus 38.6 | Minus 42.5 to minus 37.5 | Minus 40 | Minus 40 | 0.05 | 0.1 | 73 F | 68 F. or C. |
| 98.6 to 101.4 | 207.5 to 212.5 | 100 | 212 | 0.05 | 0.1 | 30 F | 32 F. or C. |
(e) Timing device.
Stop watch or other timing device graduated in divisions representing not more than 0.2 second, with an accuracy of at least ±0.05 percent when tested over intervals of 15 minutes. Electrical timing devices may be used when the current frequency is controlled to an accuracy of 0.01 percent or better.
S6.3.3Standardization.
(a) Viscometers.
Use viscometers calibrated in accordance with appendix 1 of ASTM D445-65, “Viscosity of Transparent and Opaque Liquids (Kinematic and Dynamic Viscosities).” The calibration constant, C, is dependent upon the gravitational acceleration at the place of calibration. This must, therefore, be supplied by the standardization laboratory together with the instrument constant. Where the acceleration of gravity, g, in the two locations differs by more than 0.1 percent, correct the calibration constant as follows:
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where the subscripts 1 and 2 indicate respectively the standardization laboratory and the testing laboratory.
(b) Thermometers.
Check liquid-in-glass thermometers to the nearest 0.01 °C. (0.02 °F.) by direct comparison with a standardized thermometer. Kinematic Viscosity Test Thermometers shall be standardized at “total immersion.” The ice point of standardized thermometers shall be determined before use and the official corrections shall be adjusted to conform to the changes in ice points. (See ASTM E77-66, “Verification and Calibration of Liquid-in-Glass Thermometers.”)
(c) Timers.
Time signals are broadcast by the National Bureau of Standards, Station WWV, Washington, DC at 2.5, 5, 10, 15, 20, 25, 30, and 35 Mc/sec (MHz). Time signals are also broadcast by Station CHU from Ottawa, Canada, at 3.330, 7.335, and 14.670 Mc/sec, and Station MSF at Rugby, United Kingdom, at 2.5, 5, and 10 Mc/sec.
S6.3.4Procedure. (a) Set and maintain the bath at the appropriate test temperature (see S5.1.3) within the limits specified in S6.3.2(c). Apply the necessary corrections, if any, to all thermometer readings.
(b)
Select a clean, dry, calibrated viscometer giving a flow time not less than its specified minimum, or 200 seconds, whichever is the greater.
(c)
Charge the viscometer in the manner used when the instrument was calibrated. Do not filter or dry the brake fluid, but protect it from contamination by dirt and moisture during filling and measurements.
(1)
Charge the suspended level viscometers by tilting about 30° from the vertical and pouring sufficient brake fluid through the fill tube into the lower reservoir so that when the viscometer is returned to vertical position the meniscus is between the fill marks. For measurements below 0 °C. (32 °F.), before placing the filled viscometer into the constant temperature bath, draw the sample into the working capillary and timing bulb and insert small rubber stoppers to suspend the fluid in this position, to prevent accumulation of water condensate on the walls of the critical portions of the viscometer. Alternatively, fit loosely packed drying tubes into the open ends of the viscometer to prevent water condensation, but do not restrict the flow of the sample under test by the pressures created in the instrument.
(2)
If a Cannon-Fenske Routine viscometer is used, charge by inverting and immersing the smaller arm into the brake fluid and applying vacuum to the larger arm. Fill the tube to the upper timing mark, and return the viscometer to an upright position.
(f)
At temperatures below 0 °C. (32 °F.) conduct an untimed preliminary run by allowing the brake fluid to drain through the capillary into the lower reservoir after the test temperature has been established.
(g)
Adjust the head level of the brake fluid to a position in the capillary arm about 5 mm. above the first timing mark.
(h)
With brake fluid flowing freely measure to within 0.2 second the time required for the meniscus to pass from the first timing mark to the second. If this flow time is less than the minimum specified for the viscometer, or 200 seconds, whichever is greater, repeat using a viscometer with a capillary of smaller diameter.
(i)
Repeat S6.3.4 (g) and (h). If the two timed runs do not agree within 0.2 percent, reject and repeat using a fresh sample of brake fluid.
S6.3.5Cleaning the viscometers. (a) Periodically clean the instrument with chromic acid to remove organic deposits. Rinse thoroughly with distilled water and acetone, and dry with clean dry air.
(b)
Between successive samples rinse the viscometer with ethanol (isopropanol when testing DOT 5 fluids) followed by an acetone or ether rinse. Pass a slow stream of filtered dry air through the viscometer until the last trace of solvent is removed.
S6.3.6Calculation. (a) The following viscometers have a fixed volume charged at ambient temperature, and as a consequence C varies with test temperature: Cannon-Fenske Routine, Pinkevitch, Cannon-Manning Semi-Micro, and Cannon Fenske Opaque. To calculate C at test temperatures other than the calibration temperature for these viscometers, see ASTM D2515-66, “Kinematic Glass Viscometers” or follow instructions given on the manufacturer's certificate of calibration.
S6.3.7Precision (at 95 percent confidence level ).
(a) Repeatability.
If results on duplicate samples by the same operator differ by more than 1 percent of their mean, repeat the tests.
S6.4pH value. Determine the pH value of a brake fluid by running one sample according to the following procedure.
S6.4.1Summary of the procedure. Brake fluid is diluted with an equal volume of an ethanol-water solution. The pH of the resultant mixture is measured with a prescribed pH meter assembly at 23 °C. (73.4 °F.).
S6.4.2Apparatus. The pH assembly consists of the pH meter, glass electrode, and calomel electrode, as specified in Appendices A1.1, A1.2, and A1.3 of ASTM D 1121-67, “Standard Method of Test for Reserve Alkalinity of Engine Antifreezes and Antirusts.” The glass electrode is a full range type (pH 0-14), with low sodium error.
S6.4.3Reagents. Reagent grade chemicals conforming to the specifications of the Committee on Analytical Reagents of the American Chemical Society.
(a) Distilled water.
Distilled water (S7.1) shall be boiled for about 15 minutes to remove carbon dioxide, and protected with a soda-lime tube or its equivalent while cooling and in storage. (Take precautions to prevent contamination by the materials used for protection against carbon dioxide.) The pH of the boiled distilled water shall be between 6.2 and 7.2 at 25 °C. (77 °F.).
(b) Standard buffer solutions.
Prepare buffer solutions for calibrating the pH meter and electrode pair from salts sold specifically for use, either singly or in combination, as pH standards. Dry salts for 1 hour at 110 °C. (230 °F.) before use except for borax which shall be used as the decahydrate. Store solutions with pH less than 9.5 in bottles of chemically resistant glass or polyethylene. Store the alkaline phosphate solution in a glass bottle coated inside with paraffin. Do not use a standard with an age exceeding three months.