Service Bulletin
Mack Trucks, Inc.
Greensboro, NC USA
Date Group No. Release Page
This service bulletin replaces bulletin 214-93 dated 5.2010. 7.2013
Valves and Engine injectors, Adjustment
Valves and Engine Injectors, Adjustment
Trucks
214 93 02
1(13)
MP8
PV776-89119132
W2005941
This information covers the correct procedure for adjusting the valves and engine injectors on
MACK MP8 engines.
Note: This information also applies to Mack Trucks Australia.
Contents
• “Special Tools”, page 3
• “Valves and Engine Injectors, Adjustment”, page 4
USA60336
Mack Trucks, Inc.
Service Bulletin
Note: Information is subject to change without notice.
Illustrations are used for reference only and may differ slightly from the actual engine
version. However, key components addressed in this information are represented as
accurately as possible.
Date
7.2013
Group
No. Release Page
214 93 02
2(13)
Mack Trucks, Inc.
Service Bulletin
Special Tools
For special tools ordering instructions, refer to Tool Information, Function Group 08.
T0012612
Date
7.2013
Tools
Group
No. Release Page
214 93 02
W0000416
3(13)
88800014
Flywheel Turning Tool
88880052 (part of set 88880053)
Feeler Gauges
85111377 or 88880053
Feeler Gauge Set
W2055377
Mack Trucks, Inc.
Service Bulletin
Valve cover removed
Date
7.2013
Group
214 93 02
No. Release Page
Service Procedures
Valves and Engine Injectors, Adjustment
You must read and understand the precautions and guidelines in Service Information, Function Group 20, "Engine
Safety Practices" before performing this procedure. If you
are not properly trained and certified in this procedure, ask
your supervisor for training before you perform it.
Special tools: 3949521, 85111377 or 88880053,
88800014, 88800232, 88880052
1
Note: This valves and engine injectors adjustment procedure
replaces all previous procedures including those found in
Mack MP8 Service Manuals 5-113 and 5-117.
Remove the plug from the lower right side of the flywheel
housing and install the flywheel turning tool.
4(13)
W0002368
W2005753
88800014
2
Remove the fasteners retaining the leaf springs to release
spring tension on the engine brake rocker arms. Remove leaf
springs.
Mack Trucks, Inc.
Service Bulletin
Date
7.2013
3
Camshaft Marks for Setting Valves and Engine Injectors
Group
214 93 02
No. Release Page
5(13)
• Without engine brake: Markings 1–6 apply to adjustment
of inlet valves, exhaust valves and engine injectors.
• With engine brake: Markings 1–6 apply to adjustment of
inlet valves and engine injector. Markings E1–E6 apply to
adjustment of exhaust valves.
Valve and Injector Settings with Engine Brake
W2006171
Cam
Position
5 X X
E6 X X
3 X X
E2 X X
6 X X
E4 X X
2 X X
E1 X X
4 X X
E5 X X
1 X X
E3 X X
Valve and Injector Settings without Engine Brake
Cam
Position
5 X X X
3 X X X
6 X X X
2 X X X
4 X X X
1 X X X
Injector Intake/
Exhaust
Injector Intake Exhaust
Exhaust
Engine
Brake
Engine
Brake
Rocker
Note: The “V” markings on the camshaft are for cylinder TDC
reference only and are not used for valve adjustment.
Mack Trucks, Inc.
Service Bulletin
Date
7.2013
Group
214 93 02
No. Release Page
6(13)
Intake Valves Adjustment (with or without engine brake)
4
Using the flywheel turning tool, rotate the engine to the next
camshaft marking for adjustment of the intake valve. Rotate
the engine until the valve and injector mark on the front end
of the camshaft aligns with the stamped mark on the camshaft front bearing cap.
Note: Engine must be rotated in the normal direction of operation when advancing to the next mark.
5
With the engine cold (140°F or less), check the intake valve
clearance. Push down on the back of the rocker and insert a
feeler gauge of the proper specification, 0.20 ± 0.05 mm
(0.008 ± 0.002 inch), between the bridge and the adjustment
screw. If the inlet rocker requires adjustment, loosen the lock
nut on the rocker and adjust the plunger.
T2023322
6
Hold the adjusting screw to prevent it from turning and tighten
the adjusting screw lock nut to 38 ± 4 Nm (28 ± 3 ft-lb).
7
Check the valve clearance again after the nut is tightened.
Note: Mark the rocker arm when the valve has been
adjusted.
Mack Trucks, Inc.
Service Bulletin
Date
7.2013
Group
214 93 02
No. Release Page
7(13)
Engine Injector Adjustment
8
To adjust the injector on the same cylinder location, loosen
the lock nut and back off the adjusting screw until it no longer
makes contact.
9
Adjust the engine injector's rocker arm to zero clearance.
Note: The spring must not be compressed. There should not
be any movement of the spring.
10
Tighten the adjusting screw an additional four flats or 240 degrees of clockwise rotation.
T2023323
11
Tighten the adjusting screw lock nut to 52 ± 4 Nm (38 ± 3 ftlb).
Mack Trucks, Inc.
Service Bulletin
T2022277
Date
7.2013
Group
214 93 02
No. Release Page
8(13)
Exhaust Valves Adjustment (without engine
brake)
12
Continue adjustment on the same cylinder location by checking the exhaust rocker valve clearance. Push down on the
back of the exhaust rocker and insert a 0.80 ±0.05 mm
(0.031 ±0.002 inch) feeler gauge between the bridge and the
adjustment screw. If the exhaust rocker requires adjustment,
loosen the lock nut on the rocker and adjust the plunger.
13
Hold the adjusting screw to prevent it from turning and tighten
the adjusting screw lock nut to 38 ±4 Nm (28 ±3 ft-lb).
14
Check valve clearance again after the lock nut is tightened.
Note: Mark the rocker arm when the valve has been
adjusted.
Mack Trucks, Inc.
Service Bulletin
W2006171
Date
7.2013
Group
214 93 02
No. Release Page
9(13)
Exhaust Valves Adjustment (with engine brake,
with or without shims)
15
Using the flywheel turning tool, rotate the engine to the next
camshaft marking (number plus “E”) for the adjustment of the
exhaust valves. Adjust the exhaust and brake rocker on the
cylinder number following the "E".
16
Push down on the back of the exhaust rocker and insert a
1.00 ± 0.05 mm (0.039 ± 0.002 inch) feeler gauge between
the bridge and the brake plunger.
T2023324
17
If clearance is not within specification, adjust the clearance
as required, using shims placed on top of the valve bridge.
For engines without shims, loosen the lock nut on the rocker
and adjust the plunger. Hold the adjusting screw to prevent it
from turning and tighten the adjusting screw lock nut to 38 ±4
Nm (28 ±3 ft-lb).
Note: For engines without shims, go to Step 22.
18
Remove the shim retaining screw and remove the shim.
Note: When loosening or tightening the shim retaining screw
to change the shim, the yoke must be kept fixed with a tool to
avoid bending the valve stem.
19
Make sure that the valve bridge and shim(s) are clean.
Mack Trucks, Inc.
Service Bulletin
T2009008
Date
7.2013
Group
214 93 02
No. Release Page
10(13)
20
Determine the thickness of the shim(s) required to match the
measured clearance.
Note: DO NOT use more than two shims. Shims are available in 0.05 mm (0.002 inch) increments with the thickness
marked on the surface. If two shims are required to take up
the clearance, the shims should be of nearly equal thickness.
3949521
21
Place the shim(s) in position on the valve yoke, install the retaining screw and tighten to 38 ±4 Nm (28 ±3 ft-lb).
Note: When loosening or tightening the shim retaining screw
to change the shim, the yoke must be kept fixed with a tool to
avoid bending the valve stem.
22
Check valve clearance again after lock nut is tightened or
shim is fastened. Allow feeler gauge to remain in place between the exhaust rocker arm and the valve bridge during
the following engine brake rocker check.
W2005815
Engine Brake Rocker Adjustment (with or without shims)
23
Using a 2.5 mm feeler gauge, check the exhaust brake rocker arm clearance by placing the feeler gauge between the
brake rocker arm roller and the cam lobe. The clearance
should be 2.5 ± 0.07 mm (0.1 ± 0.003 inch).
Note: 1.00 ±0.05 mm feeler gauge should still be between
exhaust rocker arm and valve bridge.
88880053
Mack Trucks, Inc.
Service Bulletin
Date
7.2013
Group
214 93 02
No. Release Page
11(13)
24
If the clearance is not within specification, loosen the brake
rocker arm lock nut (A) and turn the adjuster screw (B) 1/2 to
1 turn counter-clockwise. With the 2.5 mm feeler gauge in position between the rocker arm roller and cam lobe, tighten the
adjuster screw (B) until it makes contact and then a further 1/
2 turn until the valve yoke clearly moves down and the exhaust valve opens slightly. The engine brake mechanism is
now preloaded.
T2027091
25
Loosen the adjusting screw slowly until the 2.5 mm gauge
can be pushed in and out with some effort. Hold the adjusting
screw to prevent it from turning and tighten the lock nut to 52
± 4 Nm (38 ± 3 ft-lb).
Engine Brake Check
26
Allow 1.00 ± 0.05 mm (0.039 ± 0.002 inch) feeler gauge to remain in place between the exhaust rocker arm and the valve
bridge during the following brake rocker check.
27
Check the engine brake rocker arm clearance between the
rocker arm roller and the camshaft with the 2.5 mm feeler
gauge between the camshaft lobe and the rocker arm roller.
88880053
W2005815
28
Clearance between the camshaft and rocker roller should
meet a specification of 2.5 ± 0.07 mm (0.1 ± 0.003 inch).
Mack Trucks, Inc.
Service Bulletin
Date
7.2013
Group
214 93 02
No. Release Page
12(13)
29
If the clearance is not within the specification, the adjustment
must be repeated per the previous adjustment.
30
Check valve clearance again after the lock nut is tightened.
Note: Mark the rocker arm when the valve has been
adjusted.
31
Remove the feeler gauge from between the exhaust rocker
arm and valve bridge. Check the clearance between the
camshaft and the brake rocker roller with a 3.20 mm gauge this gauge should pass with no resistance. If there is resistance then the adjustment is incorrect. Repeat the adjustment
procedure.
88800232
32
Repeat the above procedure to adjust all other engine injectors and valve locations by rotating the engine to the next
nearest camshaft mark.
W0002368
T2022951
33
After all engine injectors and valves have been checked and
adjusted if necessary, clean the valve cover contact surface
on the cylinder head.
34
For engines with engine brake, install brake rocker leaf
springs and tighten the retaining screws on the exhaust rocker arms to 25 ± 3 Nm (18 ± 2 ft-lb). Ensure that the brake
rocker arm push rod is centered and properly seated into leaf
spring socket before tightening retaining screws.
Mack Trucks, Inc.
Service Bulletin
Date
7.2013
35
Install the valve cover. Refer to Group 211 for procedure.
36
Bring the engine to normal operating temperature. Let the engine idle for approximately 5 minutes; the system performs
its own cylinder balancing in order to attain even idling.
Note: During cylinder balancing, do not use any form of
power-consuming equipment, such as power take-off or air
conditioning.
Group
214 93 02
No. Release Page
13(13)
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