Code of Maryland Regulations › Title 11 - DEPARTMENT OF TRANSPORTATION › Subtitle 22 - MOTOR VEHICLE ADMINISTRATION-PREVENTIVE MAINTENANCE PROGRAM › Chapter 11.22.03 - Preventive Maintenance Standards for Multipurpose Passenger Vehicles and Passenger Buses › Section 11.22.03.06 - Brake System - Air

Current through Register Vol. 51, No. 14, July 12, 2024
A. Low
				Air Indicator.
Procedures:
Reject Vehicle If:
(1) Operation.
(1) Indicator fails to operate or fails to function when
						  air pressure reserve is reduced to 60 psi.
B.
				Compressor and Belt or Belts.
Procedures:
Reject Vehicle If:
(1) Inspect compressor for condition and mounting.
(1) Compressor is damaged, loose, or mounts are loose,
						  cracked, or bolts are missing.
(2) Inspect belts for presence, condition, and
						  tension.
(2) Belt is missing, broken, cracked, deteriorated, or
						  loose.
C.
				Compressor Operation. Air pressure shall be reduced to 50 psi and the engine
				started and operated at approximately 1200 rpm.
Procedures:
Reject Vehicle If:
(1) With air pressure reduced to 50 psi, observe time to
						  build pressure to 90 psi.
(1) Time required to build air pressure from 50 psi to 90
						  psi exceeds 3 minutes.
(2) Governor. (a) Cut-Out Pressure. With engine running
						  at approximately 1200 rpm, observe compressor cut-out pressure. (b) Cut-In
						  Pressure. With engine idling, deplete air pressure and observe compressor
						  cut-in pressure.
(2) (a) Cut-out pressure is greater than 135 psi. (b)
						  Cut-in pressure is less than 80 psi.
D.
				Air Leakage. Inspection for leakage shall be conducted with a fully charged
				system and brakes fully applied.
Procedures:
Reject Vehicle If:
(1) Single Vehicle. With a fully charged system, stop
						  engine and observe pressure drop in 1 minute.
(1) Air pressure drop is greater than 3 psi in 1
						  minute.
(2) Combination of Vehicles. With a fully charged system,
						  stop engine and observe pressure drop in 1 minute.
(2) Air pressure drop is greater than 4 psi in 1
						  minute.
E.
				Air Reserve.
Procedures:
Reject Vehicle If:
(1) Drop in Reservoir Pressure. With a fully charged
						  system and engine off, make one full brake application.
(1) Air pressure reservoir pressure is reduced by 30
						  percent or more on one full brake application.
F.
				Air Reservoir and Valves.
Procedures:
Reject Vehicle If:
(1) Air Reservoir. With system fully charged, open
						  primary (wet) tank drain valve and observe operation of check valve.Then open
						  drain valve on secondary (dry) tank.
(1) Check valve does not close and air is retained in the
						  secondary (dry) tank or tanks.
(2) Contamination. Observe any oil or water expelled from
						  all tanks.
(2) Any deposits of oil or water cannot be expelled.
(3) Quick Release Valves. Make full brake application and
						  release brakes.
(3) Air is not quickly exhausted through exhaust port
						  when brakes are released.
(4) Relay Valves. Apply and release brakes and observe
						  function of proper brake chambers.
(4) Air is not directed to proper brake chamber when
						  brakes are applied or air is not quickly exhausted when brakes are
						  released.
G.
				Parking and Emergency Brake Application. Vehicles with original equipment
				air-operated parking brakes are permissible. There are different systems
				designed for automatic or manual operation of the system as the design allows
				(check automatic application of brakes when air tanks are being drained).
Procedures:
Reject Vehicle If:
(1) Using park brake control valve, release air pressure
						  from brakes.
(1) Push rods are extended and vehicle can be moved.
(2) Observe if mechanism releases brakes when control
						  valve is operated.
(2) Brakes do not fully release.
H.
				Air System.
Procedures:
Reject Vehicle If:
(1) Visually inspect gladhands for condition and
						  mounting.
(1) Gladhands are damaged, have damaged seals, or are
						  insecurely mounted.
(2) Visually inspect lines and hoses for:
(a) Type.
(b) Condition.
(c) Mounting.
(2)
(a) Not an approved type.
(b) Broken, cracked, chafed, abraded, or kinked.
(c) Insecurely
						  mounted or contacting the exhaust system or any moving part.
(3) Inspect air tanks for: (a) Presence and connection.
						  (b) Condition. (c) Leaks. (d) Mounting.
(3)
(a) Tank is missing or not connected.
(b) Tank is cracked, damaged, or field repaired.
(c)
						  Tank or connections leak.
(d) Tank, mounting brackets, or springs
						  are missing, broken, cracked, or loose.
(4) Inspect drain cocks and moisture ejectors (if
						  equipped) for: (a) Presence and condition. (b) Leaks.
(4) (a) Drain cock is missing, broken, damaged, or is
						  inoperable. (b) Drain cock or moisture ejector leaks air.
I.
				Brake Mechanical Components. Do not attempt to dismantle a double diaphragm
				spring brake unit while it is on the vehicle. Utilize a safety cage and remove
				the entire unit from the vehicle. Replace with a new or rebuilt assembly. When
				rebuilding or overhauling a brake chamber, strict adherence to manufacturer's
				procedures is required. Inspect brake chamber for:
Procedures:
Reject Vehicle If:
(1) Function.
(1) Brake chamber fails to function as designed.
(2) Leaks.
(2) Brake chamber leaks or diaphragm is damaged.
(3) Damage.
(3) Brake chamber is damaged so as to affect
						  operation.
(4) Mounting.
(4) Brake chamber or mounting hardware is broken, loose,
						  damaged, or bolts are missing.
(5) Push rods.
(5) Push rod is broken, bent, or misaligned with slack
						  adjuster.
(6) Clevis yokes.
(6) Clevis yoke is broken, cracked, or worn.
(7) Clevis pins.
(7) Clevis pin is missing, worn, or cotter pin is missing
						  or an improper substitute is used.
(8) Push rod clevis pin hole setting.
(8) Except on front wheels, slack adjuster effective
						  length is not the same on all wheels.
(9) Slack adjuster.
(9) Slack adjuster is inoperative, broken, bent, or
						  extremely worn.
(10) Slack adjuster nut self-locking sleeve.
(10) Adjusting nut self-locking sleeve does not
						  function.
J.
				Slack Adjuster (Push Rod) Travel. With the assistance of a second party, make a
				treadle valve application at 85 psi in system and note rod travel.
Procedures:
Reject Vehicle If:
(1) With brakes released, inspect angle of push rod and
						  slack adjuster arm.
(1) Push rod and slack adjuster arm is less than 90
						  degrees when brakes are released.
(2) Measure push rod travel from fully released to fully
						  applied positions.
(2) Push rod travel exceeds limits in Table 1.
(3) On steering axle, inspect for difference of travel
						  between sides.
(3) Push rod travel on one side is not within 1/4 inch of
						  other side.
TABLE 1
S-CAM BRAKES-PUSH ROD TRAVEL LIMITS
(Dimensions in Inches)
Type
Effective
Area
(Sq.
						  In.)
Outside
Diameter*
(Inches)
Maximum
Stroke
(Inches)
BOLT TYPE BRAKE CHAMBER DATA
A
12
6 -15/16
1-3/8
B
24
9 -3/16
1 -3/4
C
16
8 -1/16
1 -3/4
D
6
5 -1/4
1 -1/4
E
9
6 -3/16
1 -3/8
F
36
11
2 -1/4
G
30
9 -7/8
2
ROTOCHAMBER DATA
9
9
4 -9/32
1 -1/2
12
12
4 -13/16
1 -1/2
16
16
5 -13/32
2
20
20
5 -15/16
2
24
24
6 -13/32
2
30
30
7 -1/16
2 -1/4
36
36
7 -5/8
2 -3/4
50
50
8 -7/8
3
CLAMP TYPE BRAKE CHAMBER DATA
6
6
4 -1/2
1 -1/4
9
9
5 -1/4
1 -3/8
12
12
5 -11/16
1 -3/8
16
16
6 -3/8
1 -3/4
20
20
6 -25/32
1 -3/4
24
24
7 -7/32
1 -3/4**
30
30
8 -3/32
2
36
36
9
2 -1/4
*Dimensions listed do not include cap screw
						  head
projections for rotochambers and bolt clamp
projections for clamp type brake chambers.
**2 inches for long stroke design.
BENDIX WESTINGHOUSE
DD2
2
DD3
2
K.
				Wedge Brake. With the assistance of a second party, make a full brake
				application.
Procedures:
Reject Vehicle If:
(1) Measure total shoe movement from fully released to
						  fully applied position.
(1) Brake shoe movement on wedge brakes exceeds 1/16
						  inch.
L.
				Brake Camshafts.
Procedures:
Reject Vehicle If:
(1) Inspect operation of brakes.
(1) Brake camshaft condition renders any brake
						  inoperable.
(2) Inspect travel of brake cams.
(2) Any cam is on end or turns over when brakes are
						  applied.
(3) Inspect for camshaft and bushing wear.
(3) There is more than 1/8 inch wear between camshaft and
						  bushings.
M.
				Brake Linings-Air Brakes. Visually inspect brake shoes. If shoes cannot be
				seen, removal of the lower portion of the dust cover is required.
Procedures:
Reject Vehicle If:
(1) Inspect for presence and condition of lining.
(1) Any lining is missing, cracked, broken, or not
						  securely attached to the brake shoe.
(2) Measure thickness at center of shoe. It may be
						  necessary to back off slack adjusters to make an accurate measurement.
(2) Brake lining thickness is worn to 1/4 inch or less at
						  center of shoe.
(3) Visually inspect for contamination.
(3) Lining is contaminated with oil or grease.
N.
				Brake Drums-Air Brakes.
Procedures:
Reject Vehicle If:
(1) Visually inspect for damage and cracks.
(1) Any drum contains cracks in the friction surface
						  which extend to the outer edge of the bore, or any drum contains any external
						  cracks.
(2) Removal of any wheel and brake drum in only required
						  when a rejection occurs under §N(1). When any wheel and brake drum is
						  removed, perform the inspection specified in §N(3).
(2) (Rejection not applicable in this step)
(3) Measure inside diameter of drum for wear and
						  remachining.
(3) Any combination of wear and remachining exceeds the
						  brake drum manufacturer's limits. If a limit is not available, the maximum
						  combination of wear and remachining may not exceed 0.090 inch greater than the
						  original inside diameter of the drum if the original diameter of the drum is 11
						  inches or less. For drums greater than 11 inches inside diameter, the maximum
						  wear and remachining may not exceed 0.120 inch greater than the original inside
						  diameter.
O.
				Disc Brakes-Air.
Procedures:
Reject Vehicle If:
(1) Inspect all calipers and rotor (disc) surfaces for
						  oil or grease contamination.
(1) Oil or grease is evident on accessible surfaces of
						  any caliper or rotor (disc).
(2) If brake linings are visible, visually inspect
						  thickness of lining.
(2) Brake lining thickness appears to be 1/8 inch or
						  less.
(3) If rotors (discs) are visible, visually inspect for
						  cracks or damage.
(3) Any rotor is cracked or damaged.
(4) Removal of all wheels on an axle is only required
						  when a rejection occurs under §O(2). Otherwise remove only the wheel where
						  the defect is suspected. When wheels are removed, perform the inspections
						  specified in §O(5)-(8).
(4) (Rejection not applicable in this step)
(5) Bonded Linings. (a) Measure thickness of lining at
						  thinnest point. (b) Inspect lining condition.
(5) (a) Thinnest point of remaining lining is 1/8 inch or
						  less. (b) Bonded lining is broken, cracked, loose, missing, wear is extremely
						  uneven, or lining is contaminated with oil, grease, or brake fluid.
(6) Riveted Lining. (a) Measure thickness of lining at
						  thinnest point above rivet head. (b) Inspect lining condition.
(6) (a) Thinnest point of remaining lining above a rivet
						  head is 1/8 inch or less. (b) Lining or rivet is broken, cracked, loose,
						  missing, wear is extremely uneven, or lining is contaminated with oil, grease,
						  or brake fluid.
(7) Calipers. Visually inspect for damage and
						  cracks.
(7) Caliper is leaking, fails to operate, or piston is
						  seized.
(8) Rotors (Discs). (a) Visually inspect for damage and
						  cracks. (b) Measure thickness of rotor for wear and remachining.
(8) (a) Any rotor is broken, cracked into the hub, or
						  friction surface cracks extend to the periphery of the rotor. (b) Any
						  combination of wear and remachining reduces the thickness of the rotor to less
						  than the minimum thickness established by the manufacturer or that stamped on
						  the rotor.