Emergency/Parking Brake Manual Release; Brake Chamber Removal - PREVOST H3-41 Maintenance Manual

Every 100,000 Miles (160 000 km) or once a
year, whichever comes first depending on type of
operation:
1. Disassemble and clean all parts.
2. Install new diaphragm or any other part if
worn or deteriorated.
NOTE
When the diaphragm, spring, or both are
replaced, they should be replaced in the
corresponding chamber on the same axle.
3. Perform an airtightness test:
a) Make and hold a full brake application.
b) Coat clamping ring(s) with a soapy solution.
If leakage is detected, tighten clamping ring
only enough to stop leakage. Do not over-
tighten as this can distort sealing surface or
clamping ring. Coat area around push rod
hole (loosen boot if necessary). No leakage
is permitted. If leakage is detected, the
diaphragm must be replaced.
21.2 EMERGENCY/PARKING BRAKE
MANUAL RELEASE
DANGER
Never stand in the axis line of the spring brake
chambers, especially when caging the spring.
Drive Axle
1. Block the wheels to prevent the vehicle from
moving.
2. Remove the release stud tool from its
storage place on drive axle brake air cham-
ber.
3. Remove the access plug from the end of the
spring chamber, and then insert the release
stud through the opening. Turn the release
stud 1/4 turn (clockwise) to anchor it into the
spring plate. Install the flat washer and nut,
and then turn the nut clockwise to cage the
spring. Repeat on the opposite side.
DANGER
Make sure the release stud is properly
anchored in spring plate receptacle prior to
caging the spring.
SECTION 12: BRAKE AND AIR SYSTEM
4. To manually reset the emergency/parking
brake, turn the nut counterclockwise. Rein-
stall access plugs on the spring chambers,
and release stud tools in their storage
places.
Tag Axle
1. Block the wheels to prevent the vehicle from
moving.
2. Turn the release bolt counterclockwise to
cage the power spring (approx. 2.5 inches (6
cm)). Repeat on the opposite side.
3. To manually reset the emergency/parking
brake, turn the bolt clockwise.
21.3

BRAKE CHAMBER REMOVAL

WARNING
To prevent personal injuries, brakes should be
inoperative prior to working on any of their
components.
To prevent personal injuries, brake chambers
should be made inoperative by releasing
spring tension prior to disposal.
1. Block the wheels to prevent the vehicle from
moving.
2. Safely support vehicle at the recommended
body jacking points.
3. To gain access to a given brake air
chamber, the corresponding wheel can be
removed (refer to Section 13: "Wheels, Hubs
and Tires").
4. Exhaust compressed air from system by
opening the drain valve of each reservoir.
5. For the drive and tag axles brake chambers,
manually release spring brakes (refer to
"Emergency/Parking Brake, Manual Re-
lease" procedure in this section).
6. Disconnect air line(s) from brake chamber.
7. Remove the cotter pin connecting brake
chamber and adjuster (drive axle).
8. Unbolt and remove the brake chamber from
vehicle.
PA1621 Maintenance Manual All Series | Revised June 2020 43