Alexander Dennis
Dennis Way, Guildford,
Surrey, GU1 1AF.
After Market Support Line:
0845 358 9988 (U.K.)
+44 (0) 1483 571271
Service Manual Heading:
Models Affected:
Enviro 500
North America Only
Date:

May 2014

Page:

1 of 2

Service Bulletin
Braking System
Title:

Spring Brake Chamber Breather

No:

870

Introduction
This bulletin has been issued to inform customers of the availability of an actuator by-pass
breather kit for Wabco Spring Brake Chambers. Part Numbers 441331 & 440675. These
chambers were used on chassis number 1829 onwards and also buses originally fitted with
MGM actuators but converted as per Service Bulletin 763-2.
In the event that air systems are not fully charged before attempting to move off the spring
brakes may remain lightly applied. The kit has been released to reduce the likelihood of
this, and prevent the brake from binding when vehicles are first driven each day. It will also
add a level of protection in the event of internal leakage of spring brake which is too slight
to be detected during normal maintenance checks.

Kit Details
The kit is listed under ADL Part Number 660883-2. Check availability with your local
Parts Centre.

ENSURE THAT AIR PRESSURE IS EXHAUSTED FROM THE BRAKE SYSTEM
BEFORE ATTEMPTING TO FIT BREATHER KIT. THE WORK MUST BE CARRIED
OUT BY QUALIFIED WORKSHOP PERSONNEL.

Instructions
Refer to fig 1.
1.
2.
3.
4.
5.
6.
7.
8.

Remove all dirt deposits on the brake chamber in the area where breather is to be fitted.
Remove and discard the plug (item 1) from rear of chamber.
Assembly washer (item 3) onto adapter (item 2).
Screw assembled adapter into hole where plug was removed from. Tighten to 7 ± 1 Nm.
Push breather pipe (item 5) secured with clip (item4) onto adapter (item 3).
Secure breather in place on side of chamber using strap (item 6). Tighten to 0.5 ± 0.1 Nm
Fit breather to other spring brake chamber following instructions.
Charge air brake system and check brake function correctly before returning vehicle to
service.

Last Bus Bulletin Issued: 843-5

Service Manual Heading:
Models Affected:
Enviro 500
North America Only
Date:

May 2014

Page:

2 of 2

Braking System
Title:

Spring Brake Chamber Breather

Fig 1. Breather Kit

Fig 2. Fitted Breather in Position

No:

870

Alexander Dennis
Dennis Way, Guildford,
Surrey, GU1 1AF.
After Market Support Line:
0845 358 9988 (U.K.)
+44 (0) 1483 571271
Service Manual Heading:

Braking

Models Affected:

Title:

Enviro 500
L.H.D. N. America Only
Date:
Mar 2007
Page:

Service Bulletin
No:

Replacement Brake
Actuator

763-2

1/9

This bulletin has been re-issued to inform operators that MGM type brake actuators are no
longer available. If a vehicle fitted with MGM type actuators requires a replacement
actuator, then kit no SL2099 must be used. Check with Alexander Dennis Parts for
availability. Trident 3’s are not affected as stated on previous Service Bulletin 763.
The kit facilitates the fitting of Wabco 30/30 type actuators in place of the previous MGM
units. The kit contains all necessary parts to install the Wabco actuators on both the drive
and auxiliary axle.
Important Note: MGM and Wabco actuators must not be mixed on a vehicle and it is
essential that if an original MGM actuator is being replaced with a Wabco unit, all 4
actuators on drive and auxiliary axles are changed and that the modifications are carried
out to the air brake system to maintain vehicle road legality.
SL2099 Content
Item
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

Part Number
439953
MCB-112-65P
WMC-16P
661080
440676
440677
MFN-216P
654923-1
657240
658400-4
609873
441331
440675
442163
MCS-108-25P
MCN-508P
654931
661052
612747
659280

Last Bus Bulletin Issued: 766

Qty
4
4
8
2
1
1
4
1
1
1
6
2
2
2
8
8
2
2
2
2

Description
Packer Suspension
Bolt M12 x 65
Washer Spring M16
Adaptor Elbow M/F M22
Mount Actuator LH
Mount Actuator RH
Half Nut M16
Tee Piece
Elbow 90 deg M/F
Connector Straight
Tube 3/8 Nylon Yellow
Actuator
Actuator
Plate ABS Valve
Setscrew M8 x 25
Nut Self Locking
Adaptor M22 / M16
Quick Release Valve
Plug M16
Silencer Air System

Fitting Position
Under air spring piston
Suspension piston to beam
Actuator mounting studs
In quick release valve
Drive axle RH
Drive axle LH
Actuator pushrods
In place of bracketed tee
Port In quick release valve
In end of ABS DC Valve
Between DC valve & QRV
Drive axle
Tag axle
Moves valve down
Plate to frame
Plate to frame
In ABS valve
Connected to ABS valve
In QRV port
On QRV’s

Service Manual Heading:
Models Affected:

Enviro 500
L.H.D. N. America Only
Date:
Mar 2007
Page:

Braking
Title:

No:

Replacement Brake
Actuator

763-2

2/9

Instructions
1. Ensure that the all appropriate safety measures are observed while working on the
vehicle & ensure that adequate height is available before raising the vehicle and
supporting the vehicle on stands. Ensure that all air pressure is exhausted from
brake and suspension system before commencing work.
2. While supporting the drive axle, slacken and remove the air suspension spring lower
mounting bolts. Insert the Packer (item 1) between the suspension plate and the air
spring suspension piston. Secure in position using bolts (item 2).

3. Disconnect air line connections at rear actuators. Remove clevis pin from actuating
arms. Slacken and remove actuator mounting nuts and remove actuators from
mounting brackets. On the drive axle only remove the actuator mounting brackets.
4. Mount new actuator mounting brackets (item 5) left hand and (item 6) right hand
onto the drive axle.
5. Loosen outer locknut on slack adjuster control arm brackets (View A). Ensure that a
second spanner is used to hold the inner locknut in position. It is vital that no side
loading is placed on the arm. Repeat this operation for slack adjusters on Tag and
drive axles.

Service Manual Heading:
Models Affected:

Enviro 500
L.H.D. N. America Only
Date:
Mar 2007
Page:

Braking
Title:

No:

Replacement Brake
Actuator

763-2

3/9

A
6. Fit a half nut (item 7) to the actuator pushrod, then fit clevis and adjust so that rod
end is approximately level with the inside face of the clevis. This should give a
dimension of 76mm from the centre of the clevis mounting hole to the mounting face
of the actuator. (View B). Tighten half nut to lock clevis in this position. Repeat this
operation for all replacement actuators.

7. Bolt the actuator to the mounting bracket. (Item 12) drive axle, (item 11) tag axle.
Ensure that the yoke hole is centred on the slack adjuster hole. If not, the position
of the slack adjuster should be altered by turning the adjuster hex one or two clicks
until the holes coincide.

Service Manual Heading:
Models Affected:

Title:

Enviro 500
L.H.D. N. America Only
Date:
Mar 2007
Page:

Braking
No:

Replacement Brake
Actuator

763-2

4/9

8. When the hole is correctly aligned assemble as shown in (View C). Repeat
operation for remaining actuators.

9. After tightening clevis pin nut secure with split pin. Push the control arm bracket as
far downwards as possible before retightening the outer locknut. Hold inner locknut
with a spanner to prevent twisting of the control arm.
10. Remove air fittings shown in Air Brake System - Before modification diagram.
Relocate Quick release valve to under stairs outrigger position. Fit items (8 Tee),
(9 Elbow) and (10 Connector) as shown in the Air Brake System - After modification
diagram and pipe as shown in diagram.
The new actuators are internal breathing actuators, the clear breather tube from the old
actuators that was connected to the Quick Release Valve should be removed. Cut a short
length of this breather pipe and use it to connect the QRV breather stubs together in a loop to
prevent the ingress of dirt into the valve.

Service Manual Heading:
Models Affected:

Title:

Enviro 500
L.H.D. N. America Only
Date:
Mar 2007
Page:

Braking
No:

Replacement Brake
Actuator

5/9

QUICK RELEASE VALVE POSITION, SEE PHOTO.

763-2

Service Manual Heading:
Models Affected:

Enviro 500
L.H.D. N. America Only
Date:
Mar 2007
Page:

Braking
Title:

No:

Replacement Brake
Actuator

6/9

Relocate Quick Release Valve to under stairs outrigger position.

763-2

Service Manual Heading:

Braking
Title:

Models Affected:

Enviro 500
L.H.D. N. America Only
Date:
Mar 2007
Page:

No:

Replacement Brake
Actuator

7/9

Air Brake System - Before Modification

763-2

Service Manual Heading:

Braking

Models Affected:

Title:

Enviro 500
L.H.D. N. America Only
Date:
Mar 2007
Page:

No:

Replacement Brake
Actuator

8/9

Air Brake System - After Modification

763-2

Service Manual Heading:
Models Affected:

Enviro 500
L.H.D. N. America Only
Date:
Mar 2007
Page:

Braking
Title:

No:

Replacement Brake
Actuator

763-2

9/9

11. Fit components from the kit in the positions shown in the diagram below. After
completion ensure all connections are secure. Charge air system to operating
pressure, with vehicle stationary, operate the brakes ensure that no leaks are present.