Models
680A/B
The Model 680A Jake Brake® engine retarder is designed and approved for use on Mack® E6 engines
with four-valve cylinder head configuration. The Model 680B is designed and approved for use on
Mack E7 engines. Information in this manual was current at the time of printing and is subject to
change without notice or liability.
Refer to the Installation Manual, P/N 018061, Jacobs Service Letters and instructional literature for
specific application information.
PARTS MANUAL
Models 680A and 680B Housing Assemblies
Engine Packaged
Brake Housing
Model P/N Description
680A 017045 Front housing assembly
680A 017046 Rear housing assembly
680B 01-017013 Front housing assembly
680B 01-017014 Rear housing assembly
Ill. Part Qty./
No. No. Part Name Hsg.
1 016440 Solenoid valve assembly 1
2 001081 Upper seal ring 1
3 001082 Center seal ring 1
4 001083 Lower seal ring 1
5 011930 Control valve spool assy. 3
6 012757 Control valve cover 2
7 001492 Hex head screw 5
8 010843 Stop spring 3
9 003109 Inner spring, 680A 3
9 007500 Inner spring, 680B 3
10 017008 Slave piston 3
11 013418 Outer spring 3
12 013417 Inner spring 3
13 014247 Spring retainer 3
14 001023 Retaining ring 3
15 001026 Hex nut 3
16 016997 Safety screw 3
17 014103 Master piston 3
18 002030 Flat spring 3
19 001030 Flat washer 3
20 017368 Harness 1
20
7
6
1
8
9
15
16
2
5
3
4
11
17
18
19
10
7
12
13
14
Attaching Parts Group
Ill. Part Qty./
No. No. Part Name Hsg.
013716 Hsg. Attach. Parts Grp. - 680A 1
1 013535 • Hex head bolt, SAE 12
2 013569 • Hex head bolt, SAE 6
3 013414 • Adjusting screw, SAE 6
4 013736 • Oil supply screw (3/8 x 16) 2
5 002411 • “O” ring 2
017015 Hsg. Attach. Parts Grp. - 680B 1
1 019298 • Hex head bolt, metric 12
2 017009 • Hex head bolt, metric 6
3 017011 • Adjusting screw, metric 6
4 013736 • Oil supply screw (3/8 x 16) 2
5 002411 • “O” ring 2
020453 Spacer Group, 680A & 680B 2
6 018663 • Spacer 1
7 017366 • Electrical connector 1
8 019841 • Gasket 1
NI 014690 Hose, 3/16 ID x 31 long 1
020407 Yoke Group, 680B 1
9 017710 • Yoke 6
019470 Yoke Group, 680A 1
9 017710 • Yoke 6
10 019467 • Adjusting screw 6
11 019468 • Hex nut 6
2
1
6
8
3
5
7
9
10
11
4
2 PARTS MANUAL FOR MODELS 680A/B
Control Groups
NOTE:
Controls installed by Mack Trucks, Inc. may be
different than controls supplied by Jacobs.
9
2
1
3
11
10
5
4
7
8
6
1
4
2
8
6
9
5
3
4
7
Bosch Fuel Systems, 680A & 680B Mechanical
13
16
7
9
15
4
5
14
003975 Cab Control Group
Ill. Part Qty./
No. No. Part Name Kit
1 012246 Clutch switch 1
2 012269 Switch mount bracket 1
3 005377 Pan head screw 2
4 005378 Lock washer 2
11
5 003306 Hex nut 2
6 013078 Butt splice 2
10
NI 013674 Instruction sheet 1
7 013387 Overtravel bracket* 1
8 003586 Switch, 3-position 1
9 003777 Switch plate 1
10 003707 Shrink tube 3
11 003278 Receptacle 3
NI 003781 Harness 1
NI 006833 Cable tie 12
NI 016556 Wiring diagram 1
NI 015758 Wire, 96” long 1
NI 003778 Loom 1
*Optional item not included in group
017025 Engine Control Group, 680B
017028 Fuel Pump Switch Assembly 1
1 002744 • Screw 2
2 001538 • Plain washer 2
3 001558 • Binder head screw 2
4 001559 • Lock washer 3
5 001512 • Quick disconnect tab 2
6 001534 • Mach. assy. diode 1
7 001531 • Switch clamp 1
8 017026 • Switch bracket 1
9 018188 • Switch 1
10 017029 Hex head screw 2
11 017034 Lock washer 2
NI 002014 Receptacle 2
NI 003708 Shrink tube 2
NI 003881 Harness 2
NI 017885 Connector 2
020605 Engine Control Group, 680A
017028 Fuel Pump Switch Assembly 1
1 002744 • Screw 2
2 001538 • Plain washer 2
3 001558 • Binder head screw 2
4 001559 • Lock washer 3
5 001512 • Quick disconnect tab 2
6 001534 • Mach. assy. diode 1
7 001531 • Switch clamp 1
8 017026 • Switch bracket 1
9 018188 • Switch 1
10 017029 Hex head screw 2
11 017034 Lock washer 2
NI 002014 Receptacle 2
NI 003708 Shrink tube 2
NI 003881 Harness 2
12
6
2
1
4
3
12 001180 Switch cover 1
13 002615 Actuator arm 1
14 013862 Spring wire 1
15 013863 Spring bracket 1
16 002614 Switch bracket 1
17 020624 Instruction sheet 1
NI 017885 Connector 2
NI 003778 Loom-Auto 1
UTD Fuel Systems, 680A
PARTS MANUAL FOR MODELS 680A/B 3
NI = Not Illustrated
Service Parts
Ill. Part
No. No. Part Name
1 014177 Feeler gage 0.085” (2.16 mm)
2 017397 Slave piston removal tool
3 001283 Solenoid screen retainer
4 001282 Solenoid screen
5 018781 Feeler gage 0.080” (2.03 mm)
NI 018677 680A Tune-up kit
NI 018678 680B Tune-up kit
Control System Options
Control Group for V-MAC®, 680B
Part No. Part Name Quan./Group
017945 Control group 1
V-MAC Applications
015644 Low Engine Speed Retarder Cut-off
Group (Non V-MAC applications only)
015645 Control module 1
016175 Wiring harness 1
016177 Wiring harness 1
1
2
5
3
4
CONTROL
MODULE
012260 Foot Switch Group
Installation Options
014417 Housing Attaching Parts Group
for Pre-March, 1986 Engines (680A)
(Rocker shaft holes drilled for 1/4 x 20 screws)
Part No. Part Name Quan./Group
014043 Oil supply screw (1/4 x 20) 2
002411 “O” ring 2
014104 Washer 2
014418 Instructions 1
MH Chassis Air Cleaner Adapter Kits
Part No. Description
017700 Adapter kit, Model 680B on E7 Engine
015875 Adapter kit, Model 680A on E6 Engine
Jacobs® and Jake Brake® are registered trademarks of
Jacobs Vehicle Equipment Company
22 East Dudley Town Road
Bloomfield, CT 06002
Mack® and V-MAC® are registered trademarks of Mack Trucks, Inc.
P/N 018060G ©1995 Jacobs Vehicle Equipment Company Printed in USA 8/95
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