SSeerrvviiccee BBuulllleettiinnMMaacckk TTrruucckkss,, IInncc.. TTrruucckkssGreensboro, NC USA

Date Group No. Release Page7.2012 225533 6677 0011 1(6)

Engine Compression Brake Actuator,Replacement

MP7CXU/GU

EEnnggiinnee CCoommpprreessssiioonn BBrraakkee AAccttuuaattoorr,, RReeppllaacceemmeennttThis information covers the procedures for replacing the engine compression brake actuatorfor Mack MP7 engines on MACK CXU and GU vehicles.

CCoonntteennttss• “Engine Compression Brake Actuator, Replacement”, page 2

NNoottee:: Information is subject to change without notice.Illustrations are used for reference only, and may differ slightly from the actual vehiclebeing serviced. However, key components addressed in this information are representedas accurately as possible.

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SSeerrvviiccee PPrroocceedduurreess22553333--0033--0022--0022

EEnnggiinnee CCoommpprreessssiioonn BBrraakkee AAccttuuaattoorr,, RReeppllaacceemmeennttYou must read and understand the precautions and guide-lines in Service Information, group 20, "General SafetyPractices, Engine" before performing this procedure. If youare not properly trained and certified in this procedure, askyour supervisor for training before you perform theprocedure.

11Secure the vehicle for service by parking it on a flat level sur-face, applying the parking brake, chocking the rear wheel,and placing the transmission in neutral.

22Disconnect all cables from the negative (ground) and positivebattery terminals to prevent personal injury from electricalshock and prevent damage to electrical components.

33Remove the valve cover from the engine. Refer to FunctionGroup 211, “Valve Cover, Replacement”.

44Cut the tie straps securing the fuel injector harness and movethe harness out of the way.

55Clean and dry the area around the engine compressionbrake actuator.

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66Disconnect the electrical connection from the engine com-pression brake actuator.

MMaacckk TTrruucckkss,, IInncc.. Date Group No. Release PageSSeerrvviiccee BBuulllleettiinn 7.2012 225533 6677 0011 3(6)

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1 Engine Compression Brake Actuator Assembly2 Attaching Bolts3 Oil Pipe attached

77Remove the engine compression brake actuator and the oiltube between the engine compression brake actuator androcker arm shaft.

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88Clean the cylinder head sealing surface for the engine com-pression brake actuator. Check that there is no dirt in the cyl-inder head oil gallery.

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99Replace the O-ring at the bottom of the engine compressionbrake actuator.

MMaacckk TTrruucckkss,, IInncc.. Date Group No. Release PageSSeerrvviiccee BBuulllleettiinn 7.2012 225533 6677 0011 4(6)

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1100Clean the actuator oil pipe and replace the O-rings. Lubricatethe pipe hole in the rocker arm shaft and the O-rings on thepipe with clean engine oil.

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1111Insert the oil pipe into the oil hole of the engine compressionbrake actuator.

NNoottee:: The diameter of the oil pipe is larger on one end. Makesure that the smaller end faces toward the engine compres-sion brake actuator.

NNoottee:: Make sure that the O-ring is seated fully in the enginecompression brake actuator.

MMaacckk TTrruucckkss,, IInncc.. Date Group No. Release PageSSeerrvviiccee BBuulllleettiinn 7.2012 225533 6677 0011 5(6)

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1 Engine Compression Brake Actuator Assembly2 Attaching Bolts3 Oil Pipe attached

1122Position the engine compression brake actuator on the cylin-der head.

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1133Align the oil pipe and O-ring with the hole in the rocker shaft.

1144Install the engine compression brake actuator bolts. Torqueto 24 ± 4 Nm (18 ± 3 ft-lb).

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1155Plug-in the engine compression brake actuator wiring har-ness connector.

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1166Reposition the fuel injector electrical wiring harness over theengine compression brake actuator and secure with hightemperature tie straps.

1177Install the valve cover. Refer to Function Group 211, “ValveCover, Replacement”.

1188Install all previously removed cables to the ground (negative)battery terminals.

1199Start the engine. Check for oil leaks and proper operation.

2200Close hood.